This is not a real database snapshot but set of demo screenshots. Please allow some inaccuracy in numbers and dates.

[02/17/12 05:37:27pm]    Database: rdemo16    Instance: #2 rdemo162    rrac16b.obzora.prv    10.2.0.4.0    Uptime: 10 days 18 hours 20 minutes

System Statistics

Statistic# Class Statistic Name Value
0 User logons cumulative 3224218
1 User logons current 863
2 User opened cursors cumulative 760156525
3 User opened cursors current 1198
4 User user commits 4520703
5 User user rollbacks 18626
6 User user calls 1410115240
7 User recursive calls 4533808539
8 User recursive cpu usage 125836238
9 User session logical reads 138463200952
10 User session stored procedure space 0
11 Debug CPU used when call started 345889044
12 User CPU used by this session 346224997
13 User DB time 1107549734
14 User cluster wait time 12501278
15 User concurrency wait time 34223243
16 User application wait time 201824658
17 User user I/O wait time 141607781
18 User session connect time 1328487739
19 Debug process last non-idle time 1329502685
20 User session uga memory 2196124521150088
21 User session uga memory max 3284200160144
22 Debug messages sent 13673576
23 Debug messages received 13681931
24 Debug background timeouts 4430308
25 User session pga memory 559683354448
26 User session pga memory max 1076115360208
27 Enqueue enqueue timeouts 245600
28 Enqueue enqueue waits 7657569
29 Enqueue enqueue deadlocks 2
30 Enqueue enqueue requests 357367370
31 Enqueue enqueue conversions 31058236
32 Enqueue enqueue releases 357121317
33 RAC global enqueue gets sync 260024526
34 RAC global enqueue gets async 4960112
35 RAC global enqueue get time 20570863
36 RAC global enqueue releases 229297725
37 Cache physical read total IO requests 177060800
38 Cache physical read total multi block requests 29177759
39 Cache physical read total bytes 17832886577152
40 Cache physical write total IO requests 32437589
41 Cache physical write total multi block requests 20299711
42 Cache physical write total bytes 3842092365312
43 RAC IPC CPU used by this session 0
44 RAC gcs messages sent 48015945
45 RAC ges messages sent 25388974
46 RAC global enqueue CPU used by this session 0
47 Cache db block gets 2813874976
48 Cache db block gets from cache 2812661559
49 Cache db block gets direct 1320231
50 Cache consistent gets 135649326947
51 Cache consistent gets from cache 135649315468
52 Cache consistent gets - examination 52832380926
53 Cache consistent gets direct 16327
54 Cache physical reads 184087613
55 Cache physical reads cache 181918923
56 Cache physical reads direct 2169313
57 Cache physical read IO requests 139793007
58 Cache physical read bytes 1508050837504
59 Cache db block changes 1944987884
60 Cache consistent changes 13518334884
61 Cache recovery blocks read 14723
62 Cache physical writes 46247755
63 Cache physical writes direct 5032661
64 Cache physical writes from cache 41215094
65 Cache physical write IO requests 14904730
66 Cache physical write bytes 378861608960
67 Cache physical writes non checkpoint 29887140
68 Cache summed dirty queue length 72805904
69 Cache DBWR checkpoint buffers written 25619213
70 Cache DBWR thread checkpoint buffers written 231285
71 Cache DBWR tablespace checkpoint buffers written 102941
72 Cache DBWR parallel query checkpoint buffers written 0
73 Cache DBWR object drop buffers written 2244
74 Cache DBWR transaction table writes 297918
75 Cache DBWR undo block writes 16587092
76 Cache DBWR revisited being-written buffer 253
77 Cache DBWR make free requests 0
78 Cache DBWR lru scans 0
79 Cache DBWR checkpoints 2220
80 40 DBWR fusion writes 134103
81 Cache prefetch clients - keep 0
82 Cache prefetch clients - recycle 0
83 Cache prefetch clients - default 2
84 Cache prefetch clients - 2k 0
85 Cache prefetch clients - 4k 0
86 Cache prefetch clients - 8k 0
87 Cache prefetch clients - 16k 0
88 Cache prefetch clients - 32k 0
89 Cache change write time 1396165
90 Cache redo synch writes 3985629
91 Cache redo synch time 1878734
92 Cache exchange deadlocks 126264
93 Cache free buffer requested 495527228
94 Cache dirty buffers inspected 8416238
95 Cache pinned buffers inspected 58639
96 Cache hot buffers moved to head of LRU 47694020
97 Cache free buffer inspected 196835307
98 Cache commit cleanout failures: write disabled 0
99 Cache commit cleanout failures: block lost 248460
100 Cache commit cleanout failures: cannot pin 384573
101 Cache commit cleanout failures: hot backup in progress 0
102 Cache commit cleanout failures: buffer being written 160
103 Cache commit cleanout failures: callback failure 231140
104 Cache commit cleanouts 18677150
105 Cache commit cleanouts successfully completed 17812817
106 Cache recovery array reads 0
107 Cache recovery array read time 0
108 Cache CR blocks created 187376137
109 Cache current blocks converted for CR 117086
110 Cache switch current to new buffer 321863
111 Cache write clones created in foreground 89066
112 Cache write clones created in background 45325
113 Cache write clones created for recovery 0
114 Cache physical reads cache prefetch 42815010
115 Cache physical reads prefetch warmup 49594
116 Cache prefetched blocks aged out before use 19322140
117 Cache prefetch warmup blocks aged out before use 17952
118 Cache prefetch warmup blocks flushed out before use 0
119 Cache physical reads retry corrupt 0
120 Cache physical reads direct (lob) 15459
121 Cache physical reads direct temporary tablespace 1916336
122 Cache physical writes direct (lob) 2072
123 Cache physical writes direct temporary tablespace 4920951
124 Cache cold recycle reads 0
125 Cache shared hash latch upgrades - no wait 37810260431
126 Cache shared hash latch upgrades - wait 1233565
127 Cache physical reads for flashback new 0
128 Debug calls to kcmgcs 139420518
129 Debug calls to kcmgrs 0
130 Debug calls to kcmgas 313675040
131 RAC calls to get snapshot scn: kcmgss 4255247660
132 Redo redo blocks read for recovery 457266
133 Redo redo entries 1055599861
134 Redo redo size 296968036032
135 Redo redo buffer allocation retries 7674
136 Redo redo wastage 1701886212
137 Redo redo writer latching time 27486
138 Redo redo writes 5040763
139 Redo redo blocks written 603255651
140 Redo redo write time 1458336
141 Redo redo log space requests 12241
142 Redo redo log space wait time 35056
143 Redo redo log switch interrupts 0
144 Redo redo ordering marks 12402400
145 Redo redo subscn max counts 984825
146 40 gc cr blocks served 1018540
147 40 gc cr block build time 5548
148 40 gc cr block flush time 121417
149 40 gc cr block send time 3920
150 40 gc current blocks served 2673078
151 40 gc current block pin time 235023
152 40 gc current block flush time 29308
153 40 gc current block send time 11143
154 40 gc cr blocks received 1399908
155 40 gc cr block receive time 232594
156 40 gc current blocks received 1787137
157 40 gc current block receive time 429641
158 40 gc local grants 172501334
159 40 gc remote grants 24137329
160 40 gc blocks lost 1
161 40 gc claim blocks lost 0
162 40 gc blocks corrupt 0
163 40 gc CPU used by this session 1256647
164 Cache total number of slots 0
165 RAC instance recovery database freeze count 0
166 Cache background checkpoints started 697
167 Cache background checkpoints completed 697
168 Cache number of map operations 0
169 Cache number of map misses 0
170 Redo flashback log writes 0
171 User serializable aborts 0
172 Debug transaction lock foreground requests 665
173 Debug transaction lock foreground wait time 114
174 Debug transaction lock background gets 665
175 Debug transaction lock background get time 0
176 Debug undo change vector size 99384139500
177 Debug transaction tables consistent reads - undo records applied 37234
178 Debug transaction tables consistent read rollbacks 332
179 Debug data blocks consistent reads - undo records applied 13513740422
180 Debug no work - consistent read gets 43736703510
181 Debug cleanouts only - consistent read gets 1965819
182 Debug rollbacks only - consistent read gets 57391728
183 Debug cleanouts and rollbacks - consistent read gets 130050544
184 Debug RowCR attempts 2446616264
185 Debug RowCR hits 37005274652
186 Debug RowCR - row contention 71867
187 Debug RowCR - resume 0
188 Debug rollback changes - undo records applied 156014325
189 Debug transaction rollbacks 46294
190 Debug immediate (CURRENT) block cleanout applications 5013835
191 Debug immediate (CR) block cleanout applications 132016933
192 Debug deferred (CURRENT) block cleanout applications 4027802
193 Debug commit txn count during cleanout 5745322
194 Debug active txn count during cleanout 754801551
195 Debug cleanout - number of ktugct calls 290670184
196 Debug immediate CR cleanouts (index blocks) 0
197 Debug deferred CUR cleanouts (index blocks) 0
198 Debug Commit SCN cached 7903
199 Debug Cached Commit SCN referenced 3101056
200 Debug auto extends on undo tablespace 14947
201 Debug drop segment calls in space pressure 38026
202 Debug total number of undo segments dropped 0
203 Debug doubling up with imu segment 0
204 Debug tune down retentions in space pressure 37333
205 Debug steps of tune down ret. in space pressure 36587
206 Debug space was found by tune down 24374
207 Debug space was not found by tune down 12959
208 User commit batch/immediate requested 46304
209 User commit batch requested 2
210 User commit immediate requested 46302
211 User commit batch/immediate performed 46304
212 User commit batch performed 2
213 User commit immediate performed 46302
214 User commit wait/nowait requested 0
215 User commit nowait requested 0
216 User commit wait requested 0
217 User commit wait/nowait performed 0
218 User commit nowait performed 0
219 User commit wait performed 0
220 Debug global undo segment hints helped 459
221 Debug global undo segment hints were stale 129
222 Debug local undo segment hints helped 22133
223 Debug local undo segment hints were stale 100432
224 Debug undo segment header was pinned 0
225 Debug total number of times SMON posted 1883970
226 Debug SMON posted for undo segment recovery 103
227 Debug SMON posted for txn recovery for other instances 0
228 Debug SMON posted for instance recovery 3
229 Debug SMON posted for undo segment shrink 250
230 Debug SMON posted for dropping temp segment 6
231 Debug SMON posted for supplemental logging cleanup 0
232 Debug IMU commits 0
233 Debug IMU Flushes 0
234 Debug IMU contention 0
235 Debug IMU recursive-transaction flush 0
236 Debug IMU undo retention flush 0
237 Debug IMU ktichg flush 0
238 Debug IMU bind flushes 0
239 Debug IMU mbu flush 0
240 Debug IMU pool not allocated 0
241 Debug IMU CR rollbacks 0
242 Debug IMU undo allocation size 0
243 Debug IMU Redo allocation size 0
244 Debug IMU- failed to get a private strand 0
245 Debug Misses for writing mapping 2
246 SQL table scans (short tables) 603914055
247 SQL table scans (long tables) 803
248 SQL table scans (rowid ranges) 0
249 SQL table scans (cache partitions) 6
250 SQL table scans (direct read) 0
251 SQL table scan rows gotten 2686401865639
252 SQL table scan blocks gotten 15402423343
253 SQL table fetch by rowid 113788448657
254 SQL table fetch continued row 78108841
255 SQL cluster key scans 16799774
256 SQL cluster key scan block gets 28357641
257 SQL rows fetched via callback 6186065025
258 Debug queue update without cp update 0
259 SQL index crx upgrade (prefetch) 0
260 SQL index crx upgrade (found) 2182
261 SQL index crx upgrade (positioned) 274397094
262 Debug leaf node splits 1089520
263 Debug leaf node 90-10 splits 19317
264 Debug branch node splits 5518
265 Debug failed probes on index block reclamation 267314
266 Debug recursive aborts on index block reclamation 546
267 SQL native hash arithmetic execute 0
268 SQL native hash arithmetic fail 0
269 Cache lob reads 67786
270 Cache lob writes 56174
271 Cache lob writes unaligned 56174
272 SQL index fast full scans (full) 13676
273 SQL index fast full scans (rowid ranges) 0
274 SQL index fast full scans (direct read) 0
275 Debug index fetch by key 67235297243
276 Debug index scans kdiixs1 2107637886
277 Debug queue splits 0
278 Debug queue flush 0
279 Debug queue position update 0
280 Debug queue single row 0
281 Debug queue ocp pages 0
282 Debug queue qno pages 0
283 SQL heap block compress 94004333
284 SQL sql area purged 9976884
285 SQL sql area evicted 237255
286 SQL CCursor + sql area evicted 0
287 SQL session cursor cache hits 1053091099
288 SQL session cursor cache count 33276834
289 User java call heap total size 0
290 User java call heap total size max 0
291 User java call heap used size 0
292 User java call heap used size max 0
293 User java call heap live size 0
294 User java call heap live size max 0
295 User java call heap object count 0
296 User java call heap object count max 0
297 User java call heap live object count 0
298 User java call heap live object count max 0
299 User java call heap gc count 0
300 User java call heap collected count 0
301 User java call heap collected bytes 0
302 User java session heap used size 0
303 User java session heap used size max 0
304 User java session heap live size 0
305 User java session heap live size max 0
306 User java session heap object count 0
307 User java session heap object count max 0
308 User java session heap live object count 0
309 User java session heap live object count max 0
310 User java session heap gc count 0
311 User java session heap collected count 0
312 User java session heap collected bytes 0
313 Debug cursor authentications 187639
314 RAC queries parallelized 113234
315 RAC DML statements parallelized 0
316 RAC DDL statements parallelized 0
317 RAC DFO trees parallelized 129483
318 RAC Parallel operations not downgraded 129482
319 RAC Parallel operations downgraded to serial 133740
320 RAC Parallel operations downgraded 75 to 99 pct 0
321 RAC Parallel operations downgraded 50 to 75 pct 0
322 RAC Parallel operations downgraded 25 to 50 pct 0
323 RAC Parallel operations downgraded 1 to 25 pct 0
324 RAC PX local messages sent 776957
325 RAC PX local messages recv'd 797147
326 RAC PX remote messages sent 508302
327 RAC PX remote messages recv'd 377126
328 72 buffer is pinned count 317192176626
329 72 buffer is not pinned count 35751035261
330 72 no buffer to keep pinned count 179
331 Cache table lookup prefetch client count 0
332 SQL workarea memory allocated 34555
333 SQL workarea executions - optimal 590760315
334 SQL workarea executions - onepass 509
335 SQL workarea executions - multipass 9
336 SQL parse time cpu 5098000
337 SQL parse time elapsed 10007470
338 SQL parse count (total) 1318689671
339 SQL parse count (hard) 16162898
340 SQL parse count (failures) 9974527
341 SQL frame signature mismatch 3
342 SQL execute count 3282981508
343 User bytes sent via SQL*Net to client 324703710995
344 User bytes received via SQL*Net from client 464888883948
345 User SQL*Net roundtrips to/from client 899545534
346 User bytes sent via SQL*Net to dblink 0
347 User bytes received via SQL*Net from dblink 0
348 User SQL*Net roundtrips to/from dblink 0
349 SQL sorts (memory) 1119015112
350 SQL sorts (disk) 28
351 SQL sorts (rows) 65956220765
352 Debug OTC commit optimization attempts 0
353 Debug OTC commit optimization hits 0
354 Debug OTC commit optimization failure - setup 0
355 User Workload Capture: size (in bytes) of recording 0
356 User Workload Capture: dbtime 0
357 User Workload Capture: user calls 0
358 User Workload Capture: user calls flushed 0
359 User Workload Capture: unreplayable user calls 0
360 User Workload Capture: user txns 0
361 User Workload Capture: user logins 0
362 User Workload Capture: unsupported user calls 0
363 User Workload Capture: errors 0
364 OS OS User time used 0
365 OS OS System time used 0
366 OS OS Maximum resident set size 0
367 OS OS Integral shared text size 0
368 OS OS Integral unshared data size 0
369 OS OS Integral unshared stack size 0
370 OS OS Page reclaims 0
371 OS OS Page faults 0
372 OS OS Swaps 0
373 OS OS Block input operations 0
374 OS OS Block output operations 0
375 OS OS Socket messages sent 0
376 OS OS Socket messages received 0
377 OS OS Signals received 0
378 OS OS Voluntary context switches 0
379 OS OS Involuntary context switches 0

logons cumulative

Class: User

Total number of logons since the instance started. Useful only in V$SYSSTAT. It gives an instance overview of all processes that logged on.

logons current

Class: User

Total number of current logons. Useful only in V$SYSSTAT.

opened cursors cumulative

Class: User

In V$SYSSTAT: Total number of cursors opened since the instance started.
In V$SESSTAT: Total number of cursors opened since the start of the session.

opened cursors current

Class: User

Total number of current open cursors.

user commits

Class: User

Number of user commits. When a user commits a transaction, the redo generated that reflects the changes made to database blocks must be written to disk. Commits often represent the closest thing to a user transaction rate.

user rollbacks

Class: User

Number of times users manually issue the ROLLBACK statement or an error occurs during a user's transactions.

user calls

Class: User

Number of user calls such as login, parse, fetch, or execute.
When determining activity, the ratio of user calls to RPI calls, give you an indication of how much internal work gets generated as a result of the type of requests the user is sending to Oracle.

recursive calls

Class: User

Number of recursive calls generated at both the user and system level. Oracle maintains tables used for internal processing. When Oracle needs to make a change to these tables, it internally generates an internal SQL statement, which in turn generates a recursive call.

recursive cpu usage

Class: User

Total CPU time used by non-user calls (recursive calls). Subtract this value from "CPU used by this session" to determine how much CPU time was used by the user calls.

session logical reads

Class: User

The sum of "db block gets" plus "consistent gets". This includes logical reads of database blocks from either the buffer cache or process private memory.

session stored procedure space

Class: User

Amount of memory this session is using for stored procedures.

CPU used when call started

Class: Debug

The CPU time used when the call is started.
See Also: "CPU used by this session".

CPU used by this session

Class: User

Amount of CPU time (in 10s of milliseconds) used by a session from the time a user call starts until it ends. If a user call completes within 10 milliseconds, the start and end user-call time are the same for purposes of this statistics, and 0 milliseconds are added.
A similar problem can exist in the reporting by the operating system, especially on systems that suffer from many context switches.

session connect time

Class: User

The connect time for the session in 10s of milliseconds. This value is useful only inV$SESSTAT. It is the wall clock time since the logon to this session occurred.

process last non-idle time

Class: Debug

The last time this process executed.

session uga memory

Class: User

Current UGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

session uga memory max

Class: User

Peak UGA size for a session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

messages sent

Class: Debug

Number of messages sent and received between background processes.

messages received

Class: Debug

Number of messages sent and received between background processes.

background timeouts

Class: Debug

This is a count of the times where a background process has set an alarm for itself and the alarm has timed out rather than the background process being posted by another process to do some work.

session pga memory

Class: User

Current PGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

session pga memory max

Class: User

Peak PGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT.

enqueue timeouts

Class: Enqueue

Total number of table and row locks (acquired and converted) that timed out before they could complete.

enqueue waits

Class: Enqueue

Total number of waits that occurred during an enqueue convert or get because the enqueue get was deferred.

enqueue deadlocks

Class: Enqueue

Total number of deadlocks between table or row locks in different sessions.

enqueue requests

Class: Enqueue

Total number of table or row locks acquired.

enqueue conversions

Class: Enqueue

Total number of conversions of the state of table or row lock.

enqueue releases

Class: Enqueue

Total number of table or row locks released.

physical read total IO requests

Class: Cache

Number of read requests which read one or more database blocks for all instance activity including application, backup and recovery, and other utilities. The difference between this value and "physical read total multi block requests" gives the total number of single block read requests.

physical read total multi block requests

Class: Cache

Total number of Oracle instance read requests which read in two or more database blocks per request for all instance activity including application, backup and recovery, and other utilities.

physical read total bytes

Class: Cache

Total size in bytes of disk reads by all database instance activity including application reads, backup and recovery, and other utilities. The difference between this value and "physical read bytes" gives the total read size in bytes by non-application workload.

physical write total IO requests

Class: Cache

Number of write requests which wrote one or more database blocks from all instance activity including application activity, backup and recovery, and other utilities. The difference between this stat and "physical write total multi block requests" gives the number of single block write requests.

physical write total multi block requests

Class: Cache

Total number of Oracle instance write requests which wrote two or more blocks per request to the disk for all instance activity including application activity, recovery and backup, and other utilities.

physical write total bytes

Class: Cache

Total size in bytes of all disk writes for the database instance including application activity, backup and recovery, and other utilities. The difference between this value and "physical write bytes" gives the total write size in bytes by non-application workload.

db block gets

Class: Cache

Number of times a CURRENT block was requested.
See Also: "consistent gets".

db block gets from cache

Class: Cache

Number of times a CURRENT block was requested from the buffer cache. This is a subset of "db block gets" statistics value.

db block gets direct

Class: Cache

Number of times a CURRENT block was requested bypassing the buffer cache (for example, a direct load operation). This is a subset of "db block gets" statistics value.

consistent gets

Class: Cache

Number of times a consistent read was requested for a block. See Also: "consistent changes" and "session logical reads" statistics.

consistent gets from cache

Class: Cache

Number of times a consistent read was requested for a block from buffer cache. This is a subset of "consistent gets" statistics value.

consistent gets direct

Class: Cache

Number of times a consistent read was requested for a block bypassing the buffer cache (for example, direct load operation). This is a subset of "consistent gets" statistics value.

physical reads

Class: Cache

Total number of data blocks read from disk. This value can be greater than the value of "physical reads direct" plus "physical reads cache" as reads into process private buffers also included in this statistic.

physical reads cache

Class: Cache

Total number of data blocks read from disk into the buffer cache. This is a subset of "physical reads" statistic.

physical reads direct

Class: Cache

Number of reads directly from disk, bypassing the buffer cache. For example, in high bandwidth, data-intensive operations such as parallel query, reads of disk blocks bypass the buffer cache to maximize transfer rates and to prevent the premature aging of shared data blocks resident in the buffer cache.

physical read IO requests

Class: Cache

Number of read requests for application activity (mainly buffer cache and direct load operation) which read one or more database blocks per request. This is a subset of "physical read total IO requests" statistic.

physical read bytes

Class: Cache

Total size in bytes of all disk reads by application activity (and not other instance activity) only.

db block changes

Class: Cache

Closely related to "consistent changes", this statistic counts the total number of changes that were part of an update or delete operation that were made to all blocks in the SGA. Such changes generate redo log entries and hence become permanent changes to the database if the transaction is committed.
This approximates total database work. It statistic indicates the rate at which buffers are being dirtied (on a per-transaction or per-second basis, for example).

consistent changes

Class: Cache

Number of times a user process has applied rollback entries to perform a consistent read on the block.
Work loads that produce a great deal of consistent changes can consume a great deal of resources. The value of this statistic should be small in relation to the "consistent gets" statistic.

recovery blocks read

Class: Cache

Number of blocks read during recovery.

physical writes

Class: Cache

Total number of data blocks written to disk. This statistics value equals the sum of "physical writes direct" and "physical writes from cache" values.

physical writes direct

Class: Cache

Number of writes directly to disk, bypassing the buffer cache (as in a direct load operation).

physical writes from cache

Class: Cache

Total number of data blocks written to disk from the buffer cache. This is a subset of "physical writes" statistic.

physical write IO requests

Class: Cache

Number of write requests for application activity (mainly buffer cache and direct load operation) which wrote one or more database blocks per request.

physical write bytes

Class: Cache

Total size in bytes of all disk writes from the database application activity (and not other kinds of instance activity).

physical writes non checkpoint

Class: Cache

Number of times a buffer is written for reasons other than advancement of the checkpoint. Used as a metric for determining the I/O overhead imposed by setting theFAST_START_IO_TARGET parameter to limit recovery I/Os. (Note thatFAST_START_IO_TARGET is a deprecated parameter.) Essentially this statistic measures the number of writes that would have occurred had there been no checkpointing. Subtracting this value from "physical writes" gives the extra I/O for checkpointing.

summed dirty queue length

Class: Cache

The sum of the dirty LRU queue length after every write request. Divide by write requeststo get the average queue length after write completion.

DBWR checkpoint buffers written

Class: Cache

Number of buffers that were written for checkpoints.

DBWR transaction table writes

Class: Cache

Number of rollback segment headers written by DBWR. This statistic indicates how many "hot" buffers were written, causing a user process to wait while the write completed.

DBWR undo block writes

Class: Cache

Number of rollback segment blocks written by DBWR.

DBWR revisited being-written buffer

Class: Cache

Number of times that DBWR tried to save a buffer for writing and found that it was already in the write batch. This statistic measures the amount of "useless" work that DBWR had to do in trying to fill the batch.
Many sources contribute to a write batch. If the same buffer from different sources is considered for adding to the write batch, then all but the first attempt will be "useless" because the buffer is already marked as being written.

DBWR make free requests

Class: Cache

Number of requests to DBWR to make some free buffers for the LRU.

DBWR lru scans

Class: Cache

Number of times that DBWR scans the LRU queue looking for buffers to write. This count includes scans to fill a batch being written for another purpose (such as a checkpoint). This statistic is always greater than or equal to "DBWR make free requests".

DBWR checkpoints

Class: Cache

Number of times the DBWR was asked to scan the cache and write all blocks marked for a checkpoint or the end of recovery. This statistic is always larger than "background checkpoints completed".

change write time

Class: Cache

Elapsed redo write time for changes made to CURRENT blocks in 10s of milliseconds. This statistic is populated only if TIME_STATISTICS is set to true.

redo synch writes

Class: Cache

Number of times a change being applied to the log buffer must be written out to disk due to a commit. The log buffer is a circular buffer that LGWR periodically flushes. Usually, redo that is generated and copied into the log buffer need not be flushed out to disk immediately.

redo synch time

Class: Cache

Elapsed time of all "redo synch writes" calls in 10s of milliseconds.

exchange deadlocks

Class: Cache

Number of times that a process detected a potential deadlock when exchanging two buffers and raised an internal, restartable error. Index scans are the only operations that perform exchanges.

free buffer requested

Class: Cache

Number of times a reusable buffer or a free buffer was requested to create or load a block.

dirty buffers inspected

Class: Cache

Number of dirty buffers found by the user process while the it is looking for a buffer to reuse.

pinned buffers inspected

Class: Cache

Number of times a user process, when scanning the tail of the replacement list looking for a buffer to reuse, encountered a cold buffer that was pinned or had a waiter that was about to pin it. This occurrence is uncommon, because a cold buffer should not be pinned very often.

hot buffers moved to head of LRU

Class: Cache

When a hot buffer reaches the tail of its replacement list, Oracle moves it back to the head of the list to keep it from being reused. This statistic counts such moves.

free buffer inspected

Class: Cache

Number of buffers skipped over from the end of an LRU queue in order to find a reusable buffer. The difference between this statistic and "dirty buffers inspected" is the number of buffers that could not be used because they had a user, a waiter, or were being read or written, or because they were busy or needed to be written after rapid aging out.

commit cleanout failures: write disabled

Class: Cache

Number of times a cleanout block at commit was performed but the writes to the database had been temporarily disabled.

commit cleanout failures: block lost

Class: Cache

Number of times Oracle attempted a cleanout at commit but could not find the correct block due to forced write, replacement, or switch CURRENT.

commit cleanout failures: cannot pin

Class: Cache

Total number of times a commit cleanout was performed but failed because the block could not be pinned.

commit cleanout failures: hot backup in progress

Class: Cache

Number of times Oracle attempted block cleanout at commit during hot backup. The image of the block needs to be logged before the buffer can be made dirty.

commit cleanout failures: buffer being written

Class: Cache

Number of times Oracle attempted a cleanout at commit, but the buffer was currently being written.

commit cleanouts

Class: Cache

Total number of times the cleanout block at commit function was performed.

commit cleanouts successfully completed

Class: Cache

Number of times the cleanout block at commit function completed successfully.

recovery array reads

Class: Cache

Number of reads performed during recovery.

recovery array read time

Class: Cache

Elapsed time of I/O during recovery.

CR blocks created

Class: Cache

Number of CURRENT blocks cloned to create CR (consistent read) blocks. The most common reason for cloning is that the buffer is held in a incompatible mode.

current blocks converted for CR

Class: Cache

Number CURRENT blocks converted to CR state.

switch current to new buffer

Class: Cache

Number of times the CURRENT block moved to a different buffer, leaving a CR block in the original buffer.

write clones created in foreground

Class: Cache

Number of times a background or foreground process clones a CURRENT buffer that is being written. The clone becomes the new, accessible CURRENT buffer, leaving the original buffer (now the clone) to complete writing.

write clones created in background

Class: Cache

Number of times a background or foreground process clones a CURRENT buffer that is being written. The clone becomes the new, accessible CURRENT buffer, leaving the original buffer (now the clone) to complete writing.

physical reads prefetch warmup

Class: Cache

Number of data blocks that were read from the disk during the automatic prewarming of the buffer cache.

prefetched blocks aged out before use

Class: Cache

Number of contiguous and noncontiguous blocks that were prefetched but aged out before use.

cold recycle reads

Class: Cache

Number of buffers that were read through the least recently used end of the recycle cache with fast aging strategy.

calls to kcmgcs

Class: Debug

Number of calls to routine kcmgcs to get a current SCN.

calls to kcmgrs

Class: Debug

Number of calls to routine kcsgrs to get a recent SCN.

calls to kcmgas

Class: Debug

Number of calls to routine kcmgas to get a new SCN.

calls to get snapshot scn: kcmgss

Class: RAC

Number of times a snapshot system change number (SCN) was allocated. The SCN is allocated at the start of a transaction.

redo entries

Class: Redo

Number of times a redo entry is copied into the redo log buffer.

redo size

Class: Redo

Total amount of redo generated in bytes.

redo buffer allocation retries

Class: Redo

Total number of retries necessary to allocate space in the redo buffer. Retries are needed either because the redo writer has fallen behind or because an event such as a log switch is occurring.

redo wastage

Class: Redo

Number of bytes wasted because redo blocks needed to be written before they are completely full. Early writing may be needed to commit transactions, to be able to write a database buffer, or to switch logs.

redo writer latching time

Class: Redo

Elapsed time in 10s of milliseconds needed by LGWR to obtain and release each copy latch.

redo writes

Class: Redo

Total number of writes by LGWR to the redo log files. "redo blocks written" divided by this statistic equals the number of blocks per write.

redo blocks written

Class: Redo

Total number of redo blocks written. This statistic divided by "redo writes" equals number of blocks per write.

redo write time

Class: Redo

Total elapsed time of the write from the redo log buffer to the current redo log file in 10s of milliseconds.

redo log space requests

Class: Redo

Number of times the active log file is full and Oracle must wait for disk space to be allocated for the redo log entries. Such space is created by performing a log switch.
Log files that are small in relation to the size of the SGA or the commit rate of the work load can cause problems. When the log switch occurs, Oracle must ensure that all committed dirty buffers are written to disk before switching to a new log file. If you have a large SGA full of dirty buffers and small redo log files, a log switch must wait for DBWR to write dirty buffers to disk before continuing.
Also examine the log file space and log file space switch wait events in V$SESSION_WAIT.

redo log space wait time

Class: Redo

Total elapsed waiting time for "redo log space requests" in 10s of milliseconds.

redo log switch interrupts

Class: Redo

Number of times that another instance asked this instance to advance to the next log file.

redo ordering marks

Class: Redo

Number of times that a system change number was allocated to force a redo record to have an higher SCN than a record generated in another thread using the same block.

instance recovery database freeze count

Class: RAC

Number of times the database is frozen during instance recovery.

background checkpoints started

Class: Cache

Number of checkpoints started by the background process. This statistic can be larger than "background checkpoints completed" if a new checkpoint overrides an incomplete checkpoint or if a checkpoint is currently under way. This statistic includes only checkpoints of the redo thread. It does not include:

  • Individual file checkpoints for operations such as offline or begin backup
  • Foreground (user-requested) checkpoints (for example, performed by ALTER SYSTEM CHECKPOINT LOCAL statements)

background checkpoints completed

Class: Cache

Number of checkpoints completed by the background process. This statistic is incremented when the background process successfully advances the thread checkpoint.

serializable aborts

Class: User

Number of times a SQL statement in a serializable isolation level had to abort.

transaction lock foreground requests

Class: Debug

Useful only for internal debugging purposes.

transaction lock foreground wait time

Class: Debug

Useful only for internal debugging purposes.

transaction lock background gets

Class: Debug

Useful only for internal debugging purposes.

transaction lock background get time

Class: Debug

Useful only for internal debugging purposes.

transaction tables consistent reads - undo records applied

Class: Debug

Number of undo records applied to transaction tables that have been rolled back for consistent read purposes.

transaction tables consistent read rollbacks

Class: Debug

Number of times rollback segment headers are rolled back to create consistent read blocks.

data blocks consistent reads - undo records applied

Class: Debug

Number of undo records applied to data blocks that have been rolled back for consistent read purposes.

no work - consistent read gets

Class: Debug

Number consistent gets that require neither block cleanouts nor rollbacks.
See Also: "consistent gets".

cleanouts only - consistent read gets

Class: Debug

Number of consistent gets that require only block cleanouts, no rollbacks.
See Also: "consistent gets".

rollbacks only - consistent read gets

Class: Debug

Number of consistent gets that require only block rollbacks, no block cleanouts.
See Also: "consistent gets".

cleanouts and rollbacks - consistent read gets

Class: Debug

Number of consistent gets that require both block rollbacks and block cleanouts.
See Also: "consistent gets".

rollback changes - undo records applied

Class: Debug

Number of undo records applied to user-requested rollback changes (not consistent-read rollbacks).

transaction rollbacks

Class: Debug

Number of transactions being successfully rolled back.

immediate (CURRENT) block cleanout applications

Class: Debug

Number of times cleanout records are applied immediately during current gets. Compare this statistic with "deferred (CURRENT) block cleanout applications".

immediate (CR) block cleanout applications

Class: Debug

Number of times cleanout records are applied immediately during consistent-read requests.

deferred (CURRENT) block cleanout applications

Class: Debug

Number of times cleanout records are deferred, piggyback with changes, always current get.

Commit SCN cached

Class: Debug

Number of times the system change number of a commit operation was cached.

Cached Commit SCN referenced

Class: Debug

Useful only for internal debugging purposes.

table scans (short tables)

Class: SQL

Long (or conversely short) tables can be defined by optimizer hints coming down into the row source access layer of Oracle. The table must have the CACHE option set.

table scans (long tables)

Class: SQL

Long (or conversely short) tables can be defined as tables that do not meet the short table criteria as described in table scans (short tables).

table scans (rowid ranges)

Class: SQL

During parallel query, the number of table scans conducted with specified ROWID ranges.

table scans (cache partitions)

Class: SQL

Number of range scans performed on tables that have the CACHE option enabled.

table scans (direct read)

Class: SQL

Number of table scans performed with direct read (bypassing the buffer cache).

table scan rows gotten

Class: SQL

Number of rows that are processed during scanning operations.

table scan blocks gotten

Class: SQL

During scanning operations, each row is retrieved sequentially by Oracle. This statistic counts the number of blocks encountered during the scan.
This statistic tells you the number of database blocks that you had to get from the buffer cache for the purpose of scanning. Compare this value with the value of "consistent gets" to determine how much of the consistent read activity can be attributed to scanning.

table fetch by rowid

Class: SQL

Number of rows that are fetched using a ROWID (usually recovered from an index).
This occurrence of table scans usually indicates either non-optimal queries or tables without indexes. Therefore, this statistic should increase as you optimize queries and provide indexes in the application.

table fetch continued row

Class: SQL

Number of times a chained or migrated row is encountered during a fetch.
Retrieving rows that span more than one block increases the logical I/O by a factor that corresponds to the number of blocks than need to be accessed. Exporting and re-importing may eliminate this problem. Evaluate the settings for the storage parameters PCTFREE and PCTUSED. This problem cannot be fixed if rows are larger than database blocks (for example, if the LONG datatype is used and the rows are extremely large).

cluster key scans

Class: SQL

Number of cluster scans that were started.

cluster key scan block gets

Class: SQL

Number of blocks obtained in a cluster scan.

rows fetched via callback

Class: SQL

Rows fetched via callback. Useful primarily for internal debugging purposes.

leaf node splits

Class: Debug

Number of times an index leaf node was split because of the insertion of an additional value.

branch node splits

Class: Debug

Number of times an index branch block was split because of the insertion of an additional value.

native hash arithmetic execute

Class: SQL

Number of hash operations performed using native arithmetic rather than Oracle NUMBERs.

native hash arithmetic fail

Class: SQL

Number of has operations performed using native arithmetic that failed, requiring the hash operation to be performed with Oracle NUMBERs.

lob reads

Class: Cache

Number of LOB API read operations performed in the session/system. A single LOB API read may correspond to multiple physical/logical disk block reads.

lob writes

Class: Cache

Number of LOB API write operations performed in the session/system. A single LOB API write may correspond to multiple physical/logical disk block writes.

lob writes unaligned

Class: Cache

Number of LOB API write operations whose start offset or buffer size is not aligned to the internal chunk size of the LOB. Writes aligned to chunk boundaries are the most efficient write operations. The internal chunk size of a LOB is available through the LOB API (for example, DBMS_LOB.GETCHUNKSIZE()).

index fast full scans (full)

Class: SQL

Number of fast full scans initiated for full segments.

index fast full scans (rowid ranges)

Class: SQL

Number of fast full scans initiated with rowid endpoints specified.

index fast full scans (direct read)

Class: SQL

Number of fast full scans initiated using direct read.

session cursor cache hits

Class: SQL

Number of hits in the session cursor cache. A hit means that the SQL statement did not have to be reparsed. Subtract this statistic from "parse count (total)" to determine the real number of parses that occurred.

session cursor cache count

Class: SQL

Total number of cursors cached. This statistic is incremented only ifSESSION_CACHED_CURSORS > 0. This statistic is the most useful in V$SESSTAT. If the value for this statistic in V$SESSTAT is close to the setting of the SESSION_CACHED_CURSORS parameter, the value of the parameter should be increased.

cursor authentications

Class: Debug

Number of privilege checks conducted during execution of an operation.

queries parallelized

Class: RAC

Number of SELECT statements executed in parallel.

DML statements parallelized

Class: RAC

Number of DML statements that were executed in parallel.

DDL statements parallelized

Class: RAC

Number of DDL statements that were executed in parallel.

DFO trees parallelized

Class: RAC

Number of times a serial execution plan was converted to a parallel plan.

Parallel operations not downgraded

Class: RAC

Number of times parallel execution was executed at the requested degree of parallelism.

Parallel operations downgraded to serial

Class: RAC

Number of times parallel execution was requested but execution was serial because of insufficient parallel execution servers.

Parallel operations downgraded 75 to 99 pct

Class: RAC

Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers.

Parallel operations downgraded 50 to 75 pct

Class: RAC

Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers.

Parallel operations downgraded 25 to 50 pct

Class: RAC

Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers.

Parallel operations downgraded 1 to 25 pct

Class: RAC

Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers.

PX local messages sent

Class: RAC

Number of local messages sent for parallel execution within the instance local to the current session.

PX local messages recv'd

Class: RAC

Number of local messages received for parallel execution within the instance local to the current session.

PX remote messages sent

Class: RAC

Number of remote messages sent for parallel execution within the instance local to the current session.

PX remote messages recv'd

Class: RAC

Number of remote messages received for parallel execution within the instance local to the current session.

buffer is pinned count

Class: 72

Number of times a buffer was pinned when visited. Useful only for internal debugging purposes.

buffer is not pinned count

Class: 72

Number of times a buffer was free when visited. Useful only for internal debugging purposes.

no buffer to keep pinned count

Class: 72

Number of times a visit to a buffer attempted, but the buffer was not found where expected. Like "buffer is not pinned count" and "buffer is pinned count", this statistic is useful only for internal debugging purposes.

parse time cpu

Class: SQL

Total CPU time used for parsing (hard and soft) in 10s of milliseconds.

parse time elapsed

Class: SQL

Total elapsed time for parsing, in 10s of milliseconds. Subtract "parse time cpu" from the this statistic to determine the total waiting time for parse resources.

parse count (total)

Class: SQL

Total number of parse calls (hard and soft). A soft parse is a check on an object already in the shared pool, to verify that the permissions on the underlying object have not changed.

parse count (hard)

Class: SQL

Total number of parse calls (real parses). A hard parse is a very expensive operation in terms of memory use, because it requires Oracle to allocate a workheap and other memory structures and then build a parse tree.

execute count

Class: SQL

Total number of calls (user and recursive) that executed SQL statements.

bytes sent via SQL*Net to client

Class: User

Total number of bytes sent to the client from the foreground processes.

bytes received via SQL*Net from client

Class: User

Total number of bytes received from the client over Oracle Net Services.

SQL*Net roundtrips to/from client

Class: User

Total number of Net8 messages sent to and received from the client.

bytes sent via SQL*Net to dblink

Class: User

Total number of bytes sent over a database link.

bytes received via SQL*Net from dblink

Class: User

Total number of bytes received from a database link over Oracle Net Services.

SQL*Net roundtrips to/from dblink

Class: User

Total number of Net8 messages sent over and received from a database link.

sorts (memory)

Class: SQL

Number of sort operations that were performed completely in memory and did not require any disk writes.
You cannot do much better than memory sorts, except maybe no sorts at all. Sorting is usually caused by selection criteria specifications within table join SQL operations.

sorts (disk)

Class: SQL

Number of sort operations that required at least one disk write.
Sorts that require I/O to disk are quite resource intensive. Try increasing the size of the initialization parameter SORT_AREA_SIZE. For more information, see "SORT_AREA_SIZE".

sorts (rows)

Class: SQL

Total number of rows sorted.

OS Swaps

Class: OS

Number of swap pages.

OS Signals received

Class: OS

Number of signals received.

OS Voluntary context switches

Class: OS

Number of voluntary context switches (for example, when a process gives up the CPU by a SLEEP() system call).

OS Involuntary context switches

Class: OS

Number of context switches that were enforced by the operating system.



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