Oracle 11gR1
V$SESSTAT displays user session statistics. To find the name of the statistic associated with each statistic number (STATISTIC#), query the V$STATNAME view.
| Column | Datatype | Description |
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| Session identifier |
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| Statistic number Note: Statistics numbers are not guaranteed to remain constant from one release to another. Therefore, you should rely on the statistics name rather than its number in your applications. |
|
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| Statistic value |
Note:
1.
select s.*, n.name from V$SESSTAT s, V$STATNAME n
where s.statistic# = n.statistic# and sid = 2645
order by s.value desc;
| SID | STATISTIC# | VALUE | NAME |
| 2645 | 25 | 571488 | session pga memory |
| 2645 | 26 | 571488 | session pga memory max |
| 2645 | 12 | 383153 | CPU used by this session |
| 2645 | 21 | 159688 | session uga memory max |
| 2645 | 20 | 159688 | session uga memory |
| 2645 | 39 | 32768 | physical read total bytes |
| 2645 | 58 | 32768 | physical read bytes |
| 2645 | 134 | 3340 | redo size |
| 2645 | 174 | 1024 | undo change vector size |
| 2645 | 7 | 48 | recursive calls |
2. Statistics descriptions
The statistics stored in the V$SESSTAT and V$SYSSTAT views are listed here in alphabetical order.
The CLASS column contains a number representing one or more statistics classes. The following class numbers are additive:
- 1, User
- 2, Redo
- 4, Enqueue
- 8, Cache
- 16, OS
- 32, Real Application Clusters
- 64, SQL
- 128, Debug
For example, a class value of 72 represents a statistic that relates to SQL statements and caching.
Some statistics are populated only if the TIMED_STATISTICS initialization parameter is set to true. Those statistics are flagged in the right-hand column.
| Class | Description | TIMED_ STATISTICS | |
| 8 | Number of checkpoints completed by the background process. This statistic is incremented when the background process successfully advances the thread checkpoint. | | |
| 8 | 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:
| | |
| 128 | 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. | | |
| 128 | Number of times an index branch block was split because of the insertion of an additional value | | |
| 72 | Number of times a buffer was free when visited. Useful only for internal debugging purposes. | | |
| 72 | Number of times a buffer was pinned when visited. Useful only for internal debugging purposes. | | |
| 1 | Total number of bytes received from the client over Oracle Net Services | | |
| 1 | Total number of bytes received from a database link over Oracle Net Services | | |
| 1 | Total number of bytes sent to the client from the foreground processes | | |
| 1 | Total number of bytes sent over a database link | | |
| 128 | Useful only for internal debugging purposes | | |
| 32 | Number of times a snapshot system change number (SCN) was allocated. The SCN is allocated at the start of a transaction. | | |
| 128 | Number of calls to routine kcmgas to get a new SCN | | |
| 128 | Number of calls to routine kcmgcs to get a current SCN | | |
| 128 | Number of calls to routine kcsgrs to get a recent SCN | | |
| 8 | Elapsed redo write time for changes made to CURRENT blocks in 10s of milliseconds. | 3 | |
| 128 | Number of consistent gets that require both block rollbacks and block cleanouts. | | |
| 128 | Number of consistent gets that require only block cleanouts, no rollbacks. | | |
| 64 | Number of blocks obtained in a cluster scan | | |
| 64 | Number of cluster scans that were started | | |
| 8 | Number of buffers that were read through the least recently used end of the recycle cache with fast aging strategy | | |
| 8 | Number of times Oracle attempted a cleanout at commit but could not find the correct block due to forced write, replacement, or switch CURRENT | | |
| 8 | Number of times Oracle attempted a cleanout at commit, but the buffer was currently being written | | |
| 8 | Number of times the cleanout callback function returns FALSE | | |
| 8 | Total number of times a commit cleanout was performed but failed because the block could not be pinned | | |
| 8 | 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. | | |
| 8 | Number of times a cleanout block at commit was performed but the writes to the database had been temporarily disabled | | |
| 8 | Total number of times the cleanout block at commit function was performed | | |
| 8 | Number of times the cleanout block at commit function completed successfully | | |
| 128 | Number of times the system change number of a commit operation was cached | | |
| 8 | 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. | | |
| 8 | Number of times a consistent read was requested for a block. | | |
| 8 | 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. | | |
| 8 | Number of times a consistent read was requested for a block from buffer cache. This is a subset of "consistent gets" statistics value. | | |
| 1 | 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. | 3 | |
| 128 | The CPU time used when the call is started | 3 | |
| 8 | 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. | | |
| 8 | Number CURRENT blocks converted to CR state | | |
| 128 | Number of privilege checks conducted during execution of an operation | | |
| 128 | Number of undo records applied to data blocks that have been rolled back for consistent read purposes | | |
| 8 | 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). | | |
| 8 | Number of times a CURRENT block was requested | | |
| 8 | 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. | | |
| 8 | Number of times a CURRENT block was requested from the buffer cache. This is a subset of "db block gets" statistics value. | | |
| 8 | Total number of dirty and clean buffers Oracle looks at when scanning LRU sets for dirty buffers to clean. Divide by "DBWR lru scans" to find the average number of buffers scanned. | | |
| 8 | Number of buffers that were written for checkpoints | | |
| 8 | 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". | | |
| 40 | Real Application Clusters only: Number of blocks written to satisfy a lock request from another instance | | |
| 8 | Number of clean buffers that DBWR found when it was requested to make free buffers. Divide by "DBWR make free requests" to find the average number of reusable buffers at the end of each LRU. | | |
| 8 | 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". | | |
| 8 | Number of requests to DBWR to make some free buffers for the LRU | | |
| 8 | 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. | | |
| 8 | The current scan depth (number of buffers examined by DBWR) is added to this statistic every time DBWR scans the LRU for dirty buffers. Divide by "DBWR lru scans" to find the average scan depth. | | |
| 8 | 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. | | |
| 8 | Number of rollback segment blocks written by DBWR | | |
| 32 | Number of DDL statements that were executed in parallel | | |
| 128 | Number of times cleanout records are deferred, piggyback with changes, always current get | | |
| 32 | Number of times a serial execution plan was converted to a parallel plan | | |
| 8 | Number of dirty buffers found by the user process while the it is looking for a buffer to reuse | | |
| 32 | Number of DML statements that were executed in parallel | | |
| 4 | Total number of conversions of the state of table or row lock | | |
| 4 | Total number of deadlocks between table or row locks in different sessions | | |
| 4 | Total number of table or row locks released | | |
| 4 | Total number of table or row locks acquired | | |
| 4 | Total number of table and row locks (acquired and converted) that timed out before they could complete | | |
| 4 | Total number of waits that occurred during an enqueue convert or get because the enqueue get was deferred | | |
| 8 | 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. | | |
| 64 | Total number of calls (user and recursive) that executed SQL statements | | |
| 8 | 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. | | |
| 8 | Number of times a reusable buffer or a free buffer was requested to create or load a block | | |
| 40 | Real Application Clusters only: Number of blocks that encountered a corruption or checksum failure during interconnect | | |
| 40 | Real Application Clusters only: Total time elapsed during lock converts | | |
| 40 | Number of times lock converts in the global cache timed out | | |
| 40 | Number of lock converts in the global cache | | |
| 40 | Number of log flushes of the consistent-read block | | |
| 40 | Total time spent by the BSP process in log flushes after sending a constructed consistent-read (CR) block. This statistic divided by "global cache cr blocks served" = log flush time per CR block. | | |
| 40 | Total amount of time foreground processes waited for a CR block to be sent through the interconnect. This statistic divided by "global cache cr blocks received" = time waited per block. | | |
| 40 | Total time spent by the BSP process in sending constructed consistent-read (CR) blocks. This statistic divided by "global cache cr blocks served" = send time per CR block. | | |
| 40 | Total amount of time the BSP process took to construct consistent-read (CR) blocks. This statistic divided by "global cache cr blocks served" = construction time per CR block. | | |
| 40 | Total number of blocks received | | |
| 40 | Total number of blocks constructed by the BSP process | | |
| 40 | Number of times foreground attempt to request a cr block and failed | | |
| 40 | Number of times a foreground process requested a consistent-read (CR) block when the request timed out | | |
| 40 | Number of times a lock was requested and the holder of the lock deferred the release | | |
| 40 | System configured with fewer lock elements than buffers. Number of times foreground has to wait for a lock element. | | |
| 40 | Total time spent waiting. This divided by global cache gets = time waited per request. | | |
| 40 | Number of locks acquired | | |
| 40 | Number of times a failure occurred during preparation for interconnect transfer | | |
| 32 | Total number of asynchronous global lock converts | | |
| 32 | Total number of asynchronous global lock gets | | |
| 32 | Total elapsed time in 10s of milliseconds of all synchronous and asynchronous global lock converts | | |
| 32 | Total elapsed time in 10s of milliseconds of all synchronous and asynchronous global lock gets | | |
| 32 | Total number of synchronous global lock releases | | |
| 32 | Total number of synchronous global lock converts | | |
| 32 | Total number of synchronous global lock gets | | |
| 8 | 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. | | |
| 128 | Number of times cleanout records are applied immediately during consistent-read requests | | |
| 128 | Number of times cleanout records are applied immediately during current gets. | | |
| 64 | Number of fast full scans initiated using direct read | | |
| 64 | Number of fast full scans initiated for full segments | | |
| 64 | Number of fast full scans initiated with rowid endpoints specified | | |
| 32 | Number of times the database is frozen during instance recovery | | |
| 32 | Number of times the kernel got the CURRENT SCN when there was a need to casually confirm the SCN | | |
| 32 | Number of times the kernel got a snapshot SCN without going to the distributed lock manager (DLM) | | |
| 32 | Number of times a database process is blocked waiting for a snapshot SCN | | |
| 128 | Number of times an index leaf node was split because of the insertion of an additional value | | |
| 8 | 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. | | |
| 8 | 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. | | |
| 8 | 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()). | | |
| 1 | Total number of logons since the instance started. Useful only in V$SYSSTAT. It gives an instance overview of all processes that logged on. | | |
| 1 | Total number of current logons. Useful only in V$SYSSTAT. | | |
| 128 | Number of messages sent and received between background processes | | |
| 128 | Number of messages sent and received between background processes | | |
| 64 | Number of hash operations performed using native arithmetic rather than Oracle NUMBERs | | |
| 64 | Number of has operations performed using native arithmetic that failed, requiring the hash operation to be performed with Oracle NUMBERs | | |
| 32 | Number of system change numbers obtained without going to the distributed lock manager or server | | |
| 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. | | |
| 128 | Number consistent gets that require neither block cleanouts nor rollbacks. | | |
| 1 | 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. | | |
| 1 | Total number of current open cursors | | |
| 8 | Total number of files that had to be reopened because they were no longer in the process file cache | | |
| 8 | Total number of file opens that caused a current file in the process file cache to be closed | | |
| 16 | Time spent sleeping for reasons other than misses in the data segment (see "OS Data page fault sleep time"), kernel page faults (see "OS Kernel page fault sleep time"), misses in the text segment (see "OS Text page fault sleep time"), or waiting for an OS locking object (see "OS User lock wait sleep time"). An example of such a reason is expiration of quanta. | | |
| 16 | Number of bytes read and written | | |
| 16 | Time spent sleeping due to misses in the data segment | | |
| 16 | Number of read I/Os | | |
| 16 | Number of context switches that were enforced by the operating system | | |
| 16 | Time spent sleeping due to OS kernel page faults | | |
| 16 | Number of page faults that resulted in I/O | | |
| 16 | Number of messages received | | |
| 16 | Number of messages sent | | |
| 16 | Number of page faults that did not result in an actual I/O | | |
| 16 | Total amount of time to process system traps (as distinct from system calls) | | |
| 16 | Number of write I/Os | | |
| 16 | Size of area in memory allocated by the process. Typically this represents memory obtained by way of malloc(). | | |
| 16 | Size of the process stack segment | | |
| 16 | Number of signals received | | |
| 16 | Number of swap pages | | |
| 16 | Total amount of time spent executing in system mode | | |
| 16 | Number of system calls | | |
| 16 | Time spent sleeping due to misses in the text segment | | |
| 16 | Total amount of time spent executing in user mode | | |
| 16 | Total amount of time sleeping while waiting for an OS locking object | | |
| 16 | Number of voluntary context switches (for example, when a process gives up the CPU by a SLEEP() system call) | | |
| 16 | Time spent sleeping while waiting for a CPU to become available | | |
| 32 | Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers | | |
| 32 | Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers | | |
| 32 | Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers | | |
| 32 | Number of times parallel execution was requested and the degree of parallelism was reduced because of insufficient parallel execution servers | | |
| 32 | Number of times parallel execution was requested but execution was serial because of insufficient parallel execution servers | | |
| 32 | Number of times parallel execution was executed at the requested degree of parallelism | | |
| 64 | 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. | | |
| 64 | 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. | | |
| 64 | Total CPU time used for parsing (hard and soft) in 10s of milliseconds | 3 | |
| 64 | 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. | 3 | |
| 8 | Total size in bytes of all disk reads by application activity (and not other instance activity) only. | | |
| 8 | 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. | | |
| 8 | 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. | | |
| 8 | 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. | | |
| 8 | 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. | | |
| 8 | 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. | | |
| 8 | Total number of data blocks read from disk into the buffer cache. This is a subset of "physical reads" statistic. | | |
| 8 | 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. | | |
| 8 | Number of data blocks that were read from the disk during the automatic prewarming of the buffer cache. | | |
| 8 | Total size in bytes of all disk writes from the database application activity (and not other kinds of instance activity). | | |
| 8 | Number of write requests for application activity (mainly buffer cache and direct load operation) which wrote one or more database blocks per request. | | |
| 8 | 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. | | |
| 8 | 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. | | |
| 8 | 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. | | |
| 8 | Total number of data blocks written to disk. This statistics value equals the sum of "physical writes direct" and "physical writes from cache" values. | | |
| 8 | Number of writes directly to disk, bypassing the buffer cache (as in a direct load operation) | | |
| 8 | Total number of data blocks written to disk from the buffer cache. This is a subset of "physical writes" statistic. | | |
| 8 | 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 the FAST_START_IO_TARGET parameter to limit recovery I/Os. (Note that FAST_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. | | |
| 8 | 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. | | |
| 8 | Number of contiguous and noncontiguous blocks that were prefetched | | |
| 8 | Number of contiguous and noncontiguous blocks that were prefetched but aged out before use | | |
| 128 | The last time this process executed | 3 | |
| 32 | Number of local messages received for parallel execution within the instance local to the current session | | |
| 32 | Number of local messages sent for parallel execution within the instance local to the current session | | |
| 32 | Number of remote messages received for parallel execution within the instance local to the current session | | |
| 32 | Number of remote messages sent for parallel execution within the instance local to the current session | | |
| 32 | Number of SELECT statements executed in parallel | | |
| 8 | Elapsed time of I/O during recovery | | |
| 8 | Number of reads performed during recovery | | |
| 8 | Number of blocks read during recovery | | |
| 8 | Number of blocks read for lost write checks during recovery. | | |
| 8 | Number of Block Read Records that skipped the lost write check during recovery. | | |
| 1 | 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. | | |
| 1 | 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. | | |
| 2 | Number of exclusive redo blocks that were checksummed by the generating foreground processes. An exclusive redo block is the one whose entire redo content belongs to a single redo entry. | | |
| 2 | Number of redo blocks that were checksummed by the LGWR. | | |
| 2 | Total number of redo blocks written. This statistic divided by "redo writes" equals number of blocks per write. | | |
| 2 | 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. | | |
| 2 | Number of times a redo entry is copied into the redo log buffer | | |
| 2 | Number of times a Block Read Record is copied into the log buffer. | | |
| 2 | 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 | | |
| 2 | Total elapsed waiting time for "redo log space requests" in 10s of milliseconds | 3 | |
| 2 | Number of times that a system change number was allocated to force a redo record to have a higher SCN than a record generated in another thread using the same block | | |
| 2 | Total amount of redo generated in bytes | | |
| 2 | Total amount of Block Read Records generated in bytes. | | |
| 8 | Elapsed time of all "redo synch writes" calls in 10s of milliseconds | 3 | |
| 8 | 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. | | |
| 2 | 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. | | |
| 2 | Total elapsed time of the write from the redo log buffer to the current redo log file in microseconds | 3 | |
| 2 | Elapsed time in 10s of milliseconds needed by LGWR to obtain and release each copy latch | 3 | |
| 2 | 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 | | |
| 40 | Number of times this instance wrote a rollback segment so that another instance could read it | | |
| 40 | Number of times this instance wrote a undo header block so that another instance could read it | | |
| 128 | Number of undo records applied to user-requested rollback changes (not consistent-read rollbacks) | | |
| 128 | Number of consistent gets that require only block rollbacks, no block cleanouts. | | |
| 64 | Rows fetched via callback. Useful primarily for internal debugging purposes. | | |
| 1 | Number of times a SQL statement in a serializable isolation level had to abort | | |
| 1 | The connect time for the session in 10s of milliseconds. This value is useful only in V$SESSTAT. It is the wall clock time since the logon to this session occurred. | 3 | |
| 64 | Total number of cursors cached. This statistic is incremented only if SESSION_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. | | |
| 64 | 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. | | |
| 1 | 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. | | |
| 1 | Current PGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT. | | |
| 1 | Peak PGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT. | | |
| 1 | Amount of memory this session is using for stored procedures | | |
| 1 | Current UGA size for the session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT. | | |
| 1 | Peak UGA size for a session. Useful only in V$SESSTAT; it has no meaning in V$SYSSTAT. | | |
| 128 | Number of unsuccessful buffer gets from the shared I/O pool from instance startup time. | | |
| 128 | Number of successful buffer gets from the shared I/O pool from instance startup time. | | |
| 64 | 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. | | |
| 64 | 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. | | |
| 64 | Total number of rows sorted | | |
| 1 | Total number of Oracle Net Services messages sent to and received from the client | | |
| 1 | Total number of Oracle Net Services messages sent over and received from a database link | | |
| 8 | The sum of the dirty LRU queue length after every write request. Divide by write requests to get the average queue length after write completion. | | |
| 8 | Number of times the CURRENT block moved to a different buffer, leaving a CR block in the original buffer | | |
| 64 | 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. | | |
| 64 | 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). | | |
| 64 | 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. | | |
| 64 | Number of rows that are processed during scanning operations | | |
| 64 | Number of range scans performed on tables that have the CACHE option enabled | | |
| 64 | Number of table scans performed with direct read (bypassing the buffer cache) | | |
| 64 | 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) | | |
| 64 | During parallel query, the number of table scans conducted with specified ROWID ranges | | |
| 64 | 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. | | |
| 8 | Total number of file opens performed by the instance. Each process needs a number of files (control file, log file, database file) in order to work against the database. | | |
| 128 | Useful only for internal debugging purposes | | |
| 128 | Useful only for internal debugging purposes | | |
| 128 | Useful only for internal debugging purposes | | |
| 128 | Useful only for internal debugging purposes | | |
| 128 | Number of transactions being successfully rolled back | | |
| 128 | Number of times rollback segment headers are rolled back to create consistent read blocks | | |
| 128 | Number of undo records applied to transaction tables that have been rolled back for consistent read purposes | | |
| 32 | Total number of times that the process cleanup was performed unnecessarily because the session or process did not get the next batched SCN. The next batched SCN went to another session instead. | | |
| 1 | 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. | | |
| 1 | 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. | | |
| 1 | Number of times users manually issue the ROLLBACK statement or an error occurs during a user's transactions | | |
| 8 | 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. | | |
| 8 | 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. | |
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