Oracle8 Reference Release 8.0 A58242-01 |
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The V$SESSION_WAIT view displays the events for which sessions have just completed waiting or are currently waiting. The V$SYSTEM_EVENT displays the total number of times all the sessions have waited for the events in that view. The V$SESSION_EVENT is similar to V$SYSTEM_EVENT, but displays all waits for each session. For more information on these views, see "V$SESSION_EVENT" on page 3-85, "V$SESSION_WAIT" on page 3-88, and "V$SYSTEM_EVENT" on page 3-107.
Many of these wait events are tied to the internal implementation of Oracle and therefore are subject to change or deletion without notice. This may even happen during a bug fix patch release. Application developers should be aware of this and write their code to tolerate missing or extra wait events.
This appendix describes the event name, wait time, and parameters for each event. The following SQL statement displays all Oracle events:
SELECT * FROM V$EVENT_NAME;
The following wait events are present in the Oracle Server. The columns P1, P2, and P3 represent parameters for the wait event.
This section describes a number of common event parameters.
This is the block number of the block for which Oracle needs to wait. The block number is relative to the start of the file. To find the object to which this block belongs, enter these SQL statements:
select name, kind from ext_to_obj_view where file# = file# and lowb <= block# and highb >= block#;
The number of blocks that is being either read from or written to the file. The block size is dependent on the file type:
If the value for this parameter equals 0, a reset was sent to the client. A non-zero value indicates that a break was sent to the client.
The class of the block describes how the contents of the block are used. For example, class 1 represents data block, class 4 represents segment header.
The initials "dba" represents the data block address. A dba consists of a file number and a block number.
The address of the disconnect function of the driver that is currently being used.
The following query returns the name of the database file:
select * from v$datafile where file# = file#;
The first identifier (id1) of the enqueue or global lock takes its value from P2 or P2RAW. The meaning of the identifier depends on the name (P1).
The second identifier (id2) of the enqueue or global lock takes its value from P3 or P3RAW. The meaning of the identifier depends on the name (P1).
The relative index number into V$LOCK_ELEMENT.
The mode is usually stored in the low order bytes of P1 or P1RAW and indicates the mode of the enqueue or global lock request. This parameter has one of the following values:
Mode Value | Description |
1 |
Null mode |
2 |
Sub-Share |
3 |
Sub-Exclusive |
4 |
Share |
5 |
Share/Sub-Exclusive |
6 |
Exclusive |
Use the following SQL statement to retrieve the name of the lock and the mode of the lock request:
select chr(bitand(p1,-16777216)/16777215)|| chr(bitand(p1, 16711680)/65535) "Lock", bitand(p1, 65536) "Mode" from v$session_wait where event = `DFS enqueue lock acquisition';
The name or "type" of the enqueue or global lock can be determined by looking at the two high order bytes of P1 or P1RAW. The name is always two characters. Use the following SQL statement to retrieve the lock name.
select chr(bitand(p1,-16777216)/16777215)|| chr(bitand(p1,16711680)/65535) "Lock" from v$session_wait where event = `DFS enqueue lock acquisition';
The name of the object namespace as it is displayed in V$DB_OBJECT_CACHE view.
The number of I/Os that are "requested". This differs from the number of blocks in that one request could potentially contain multiple blocks.
The number of the inactive session. Use the following SQL statement to find more information about the session:
select * from v$session where sid = session#;
This is the total amount of time the session has waited for this session to die.
This section describes the Oracle events.
This event occurs only for the DBWR in the Parallel Server. Each DBWR of every instance holds a global lock on each file in shared mode. The instance that is trying to offline the file will escalate the global lock from shared to exclusive. This signals the other instances to synchronize their SGAs with the controlfile before the file can be taken offline. The name of this lock is DF (see Appendix B, "Enqueue and Lock Names" for more information).
Wait Time: 1 second in loop. The DBWR is waiting in a loop (sleep, check) for the other instances to downgrade to NULL mode. During this time, the DBWR cannot perform other tasks such as writing buffers.
file |
See "file#" on page A-8. |
The session waits for the lock handle of a global lock request. The lock handle identifies a global lock. With this lock handle, other operations can be performed on this global lock (to identify the global lock in future operations such as conversions or release). The global lock is maintained by the DLM.
Wait Time: The session waits in a loop until it has obtained the lock handle from the DLM. Inside the loop there is a wait of 0.5 seconds.
Parameters:
name |
|
mode |
See "mode" on page A-8. |
id1 |
See "id1" on page A-8. |
id2 |
See "id2" on page A-8. |
The session needs to get the lock handle.
The session waits for an external large object (LOB) to close.
Wait Time: The total elapsed time for the close call.
Parameters:
session# |
|
waited |
See "waited" on page A-9. |
The session waits to check if an external large object (LOB) exists.
Wait Time: The total elapsed time for the exists call.
Parameters:
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
The session waits to check if an external large object (LOB) has already been opened.
Wait Time: The total elapsed time for the isopen call.
Parameters:
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
The session waits on a call to check the size of an external large object (LOB).
Wait Time: The total elapsed time for the call to check the LOB size.
Parameters:
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
The session waits on a call to find or generate the external name of a external large object.
Wait Time: The total elapse time for make external file name to complete.
Parameters:
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
The session is waiting on a call to find or generate the external path name of an external large object (LOB).
Wait Time: The total elapsed time for make external path to complete.
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
The session waits on a call to open the external large object (LOB).
Wait Time: The total elapsed time for the open call to complete.
Parameters:
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
The session waits for a read from a external large object (LOB) to complete.
Wait Time: The total elapse time for the read to complete.
Parameters:
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
The session waits for a positioning call within the external large object (LOB) to complete.
Wait Time: The total elapse time for the seek to complete.
Parameters:
session# |
See "session#" on page A-9. |
waited |
See "waited" on page A-9. |
This event is called through the DBMSLOCK.SLEEP procedure or USERLOCK.SLEEP procedure. This event will most likely originate from procedures written by a user.
Wait Time: The wait time is in hundredths of seconds and is dependent on the user context.
Parameter:
duration |
The duration that the user specified in the DBMS_LOCK.SLEEP or USER_LOCK.SLEEP procedures. |
The server sends a break or reset message to the client. The session running on the server waits for a reply from the client.
Wait Time: The actual time it takes for the break or reset message to return from the client.
Parameters:
driver id |
|
break? |
See "break?" on page A-7. |
Same as SQL*Net break/reset to client, but in this case, the break/reset message is sent to another server process over a database link.
Wait Time: The actual time it takes for the break or reset message to return from the other server process.
driver id |
|
break? |
See "break?" on page A-7. |
The server process (foreground process) waits for a message from the client process to arrive.
Wait Time: The time it took for a message to arrive from the client since the last message was sent to the client.
driver id |
|
#bytes |
The number of bytes received by the server (foreground process) from the client. |
The session waits while the server process (foreground process) receives messages over a database link from another server process.
Wait Time: The time it took for a message to arrive from another server (foreground process) since a message was sent to the other foreground process.
Parameters:
driver id |
|
#bytes |
The number of bytes received by the server (foreground process) from another foreground process over a database link. |
The server (foreground process) is sending a message to the client.
Wait Time: The actual time the send takes.
Parameters:
driver id |
|
#bytes |
The number of bytes sent by the server process to the client. |
The server process (foreground process) is sending a message over a database link to another server process.
Wait Time: The actual time the send takes.
Parameters:
driver id |
|
#bytes |
The number of bytes sent by the server process to another server process over a database link. |
The server is performing another send to the client. The previous operation was also a send to the client.
Wait Time: The time waited depends on the time it took to receive the data (including the waiting time).
Parameters:
driver id |
|
#bytes |
The number of bytes received from the client. |
The foreground process is expecting more data from a data base link.
Wait Time: The total time it takes to read the data from the database link (including the waiting time for the data to arrive).
driver id |
|
#bytes |
The number of bytes received. |
The server process is sending more data/messages to the client. The previous operation to the client was also a send.
Wait Time: The actual time it took for the send to complete.
Parameters:
driver id |
|
#bytes |
The number of bytes that are being sent to the client. |
The event indicates that the server is sending data over a database link again. The previous operation over this database link was also a send.
Wait Time: The actual time it takes to send the data to the other server.
Parameters:
driver id |
|
#bytes |
The number of bytes that are sent over the database link to the other server process. |
WMON is the UNIX-specific Wait Monitor, that can be used to reduce the number of system calls related to setting timers for posting or waiting in Oracle. You need to set an initialization parameter that enables the WMON process.
Wait Time: Depends on the next timeout.
Parameters: none
A session has issued an alter system set mts_dispatchers=<string> and it waiting for the dispatchers to get started.
Wait Time: The session will wait 1/100 of a second and check to see if the new dispatchers have started else the session will wait again.
Parameters:
waited |
The number of times that the session has waited 1/100 of second. |
A session is waiting on another process to allocate an System Change Number (SCN). If the foreground timed out waiting on a process to get the SCN, the foreground will get the SCN.
Wait Time: The wait time is 1 second on the assumption that an SCN allocation should normally need much less than that.
Parameters: none
Wait until a buffer becomes available. This event happens because a buffer is either being read into the buffer cache by another session (and the session is waiting for that read to complete) or the buffer is the buffer cache, but in a incompatible mode (that is, some other session is changing the buffer).
Wait Time: Normal wait time is 1 second. If the session was waiting for a buffer during the last wait, then the next wait will be 3 seconds.
Parameters:
file# |
See "file#" on page A-8. |
block# |
See "block#" on page A-7. |
id |
The buffer busy wait event is called from different places in the session. Each place in the kernel points to different reason, as described in |
Oracle does not really wait on this event; the foreground only yields the CPU. Thus, the chances of catching this event are very low. This is not an application induced deadlock, but an assumed deadlock by the cache layer. The cache layer cannot get a buffer in a certain mode within a certain amount of time.
Wait Time: 0 seconds. The foreground process only yields the CPU and will usually be placed at the end of the CPU run queue.
Parameters:
class |
See "class" on page A-7. |
mode |
See "mode" on page A-8. |
flag |
The flag points to the internal flags used by the session to get this block. |
dba |
See "dba" on page A-7. |
The buffer could not be checkpointed, because some process is modifying it. This means that after the wait, the DBWR will scan the whole buffer cache again. This could happen during a database close or after a user does a local checkpoint. During this situation the database cannot be closed.
Wait Time: 1 second
Parameters:
dba |
See "dba" on page A-7. |
state |
State refers to the status of the buffer contents. |
mode |
See "mode" on page A-8. |
buffer# |
This is the index of the block in the buffer cache (V$BH). |
The session waits on the buffer hash chain latch. Primarily used in the dump routines.
Wait Time: 1 second
Parameters:
This event occurs only if the instance is mounted in shared mode (Parallel Server). During the read of the buffer, the contents changed. This means that either:
The block will be re-read (this may fail up to 3 times), then corruption is assumed and the corrupt block is dumped in the trace file.
Wait Time: The wait time is the elapsed time of the read.
Parameters::
file# |
See "file#" on page A-8. |
block# |
See "block#" on page A-7. |
A session waits for a checkpoint to complete. This could happen, for example, during a close database or a local checkpoint.
Wait Time: 5 seconds
Parameters: none
During a range checkpoint operation a buffer was found that was not saved or written. Either:
Wait Time: 10 milliseconds
Parameters: none
This event occurs while the session is writing physical blocks to all controlfiles. This happens when:
Wait Time: The wait time is the time it takes to finish all writes to all controlfiles.
Parameters:
Reading from the controlfile. This happens in many cases. For example, while:
Wait Time: The wait time is the elapsed time of the read.
Parameters:
This wait is signaled while the controlfile's shared information is written to disk. This is an atomic operation protected by an enqueue (CF), so that only one session at a time can write to the entire database.
Wait Time: The wait time is the elapsed time of the write.
Parameters:
This event occurs during a the creation of a Version 7 controlfile as part of converting a database to Version 7 from Version 6.
Wait Time: The wait time is the elapsed time of the read.
Parameters:
This happens during recovery. Database blocks that need to be changed as part of recovery are read in parallel from the database.
Wait Time: Wait until all of the I/Os are completed.
Parameters:
This event occurs in the DBWR. It indicates that the DBWR is performing a parallel write to files and blocks. The parameter requests indicates the real number of I/Os that are being performed. When the last I/O has gone to disk, the wait ends.
Wait Time: Wait until all of the I/Os are completed.
Parameters:
Similar to db file sequential read, except that the session is reading multiple data blocks.
Wait Time: The wait time is the actual time it takes to do all of the I/Os.
Parameters:
file# |
See "file#" on page A-8. |
block# |
See "block#" on page A-7. |
blocks |
The number of blocks that the session is trying to read from the file# starting at block#. |
The session waits while a sequential read from the database is performed. This event is also used for rebuilding the controlfile, dumping datafile headers, and getting the database file headers.
Wait Time: The wait time is the actual time it takes to do the I/O.
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
blocks |
This is the number of blocks that the session is trying to read (should be 1). |
This event is used to wait for the writing of the file headers.
Wait Time: The wait time is the actual time it takes to do the I/O.
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
blocks |
This is the number of blocks that the session is trying to write in file# starting at block#. |
During Direct Path operations the data is asynchronously read from the database files. At some stage the session needs to make sure that all outstanding asynchronous I/O have been completed to disk. This can also happen if during a direct read no more slots are available to store outstanding load requests (a load request could consist of multiple I/Os).
Wait Time: 10 seconds. The session will be posted by the completing asynchronous I/O. It will never wait the entire 10 seconds. The session waits in a tight loop until all outstanding I/Os have completed.
Parameters:
During Direct Path operations the data is asynchronously written to the database files. At some stage the session needs to make sure that all outstanding asynchronous I/O have been completed to disk. This can also happen if during a direct write no more slots are available to store outstanding load requests (a load request could consist of multiple I/Os).
Wait Time: 10 seconds. The session will be posted by the completing asynchronous I/O. It will never wait the entire 10 seconds. The session waits in a tight loop until all outstanding I/Os have completed.
Parameters:
During shutdown immediate or normal, the shutdown process must wait for all the dispatchers to shutdown. As each dispatcher is signaled, the session that causes the shutdown is waits on this event until the requested dispatcher is no longer alive.
Wait Time: 1 second
Parameter:
waited |
Indicates the cumulative wait time. After 5 minutes, the session writes to the alert and trace files to indicate that there might be a problem. |
This basically means that the dispatcher is idle and waiting for some work to arrive.
Wait Time: 60 seconds
Parameter:
It is possible for a race condition to occur when creating a new cluster key. If it is found that another process has put the cluster key into the data/index block, then the session waits and retries. The retry should then find a valid cluster key.
Wait Time: 0.01 seconds
Parameter:
dba |
The dba of the block into which the session is trying to insert a cluster key. |
The session is waiting for a local enqueue. The wait is dependent on the name of the enqueue (see Appendix B, "Enqueue and Lock Names").
Wait Time: Depends on the enqueue name.
Parameters:
name |
|
mode |
See "mode" on page A-8. |
The time it takes to identify a file so that it can be opened later.
The time it takes to open the file.
This will happen if:
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-8. |
block# |
See "block#" on page A-7. |
The session is waiting for a free slot in the global transaction table (used by the Distributed Database Option). It will wait for 1 second and try again.
Wait Time: 1 second
Parameter:
tries |
The number of times the session tried to find a free slot in the global transaction table. |
Used during the creation of a process. The session will scan the process table and look for a free process slot. If none can be found, PMON is posted to check if all the processes currently in the process table are still alive. If there are dead processes, PMON will clean them and make the process slot available to new processes. The waiting process will then rescan the process table to find the new slot.
Wait Time: 1 second
Parameters: none
All releasable locks are used and a new one has been requested. To make a lock element available, a lock element is pinged.
Wait Time: The duration of the lock get operation to ping the lock element.
Parameter:
lenum |
See "lenum" on page A-8. |
The session waits to convert a buffer up from Shared Current to Exclusive Current status.
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
lenum |
See "lenum" on page A-8. |
PMON is waiting for an LCK process to cleanup the lock context after a foreground process died while doing a global cache lock operation.
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
lenum |
See "lenum" on page A-8. |
The session waits for a lock convert from NULL to SHARED mode on the block identified by file# and block#.
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
class |
See "class" on page A-7. |
The session waits for a lock convert from NULL to EXCLUSIVE mode on the block identified by file# and block#.
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
lenum |
See "lenum" on page A-8. |
The session waits for a lock get in NULL mode on the block identified by file# and block#.
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
class |
See "class: on page A-6. |
The session waits for a lock get in SHARED mode on the block identified by file# and block#.
Wait Time: 1 second
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
class |
See "class: on page A-7. |
The session waits for a lock get in SUB SHARED mode on the block identified by file# and block#.
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
lenum |
See "lenum" on page A-8. |
The session waits for a lock get in EXCLUSIVE mode on the block identified by file# and block#.
Wait Time: 1 second
Parameters:
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
lenum |
See "lenum" on page A-8. |
The session waits for a lock convert from SHARED to EXCLUSIVE mode on the block identified by file# and block#.
Wait Time: 1 second
file# |
See "file#" on page A-7. |
block# |
See "block#" on page A-6. |
lenum |
See "lenum" on page A-8. |
This event is used for two purposes:
If a time-out period has been specified, then wait that amount of time for the session to be detached.
From either KILL SESSION or internal request. Having posted a session that it should kill itself, wait for up to 1 minute for the session to die.
Wait Time: 1 second
Parameters:
session# |
|
waited |
See "waited" on page A-9. |
The session waits for a transaction branch that is currently used by another session.
Wait Time: 1 second
Parameters:
branch# |
The serial number of the transaction for which the session is waiting. |
waited |
See "waited" on page A-9. |
While trying to find an index key in an index block, Oracle noticed that the index block was being split. Oracle will wait for the split to finish and try to find the key again.
Wait Time: The session will yield the CPU, so there is no actual waiting time.
Parameters:
The session waits for SMON to finish the instance, transaction recovery, or sort segment cleanup.
Wait Time: The wait time can vary and depends on the amount of recovery needed.
Parameter:
undo segment# |
If the value is 0, SMON is probably performing instance recovery. If P1 > 0, use this query to find the undo segment: select * from v$rollstat where usn = undo segment#; |
The session waits for SMON to enable or disable cache or transaction recovery. This usually happens during ALTER DATABASE OPEN or CLOSE.
Wait Time: Wait time depends on the amount of time the action takes (that is, the amount of recovery needed).
The session waits for an I/O to complete or it waits for a slave process to become available to submit the I/O request. This event occurs on platforms that do not support asynchronous I/O.
Wait Time: 50 milliseconds
Parameter:
msg ptr |
A pointer to the I/O request. |
The session waits for the background LCK process(es) to finish what they are doing. For example:
Wait Time: 10 seconds
Parameters:
count |
The number of LCK processes that have finished. |
loops |
The number times the process had to wait for the LCK processes to finish what they were doing. |
This event is used as part of the process of determining whether a latch needs to be cleaned.
Wait Time: 0.05 to 0.1 seconds
Parameters:
The process waits for a latch that is currently busy (held by another process).
Wait Time: The wait time increases exponentially and does not include spinning on the latch (active waiting). The maximum wait time also depends on the number of latches that the process is holding. There is an incremental wait of up to 2 seconds.
Parameters:
The session tries to find the load lock for the database object so that it can load the object. The load lock is always obtained in Exclusive mode, so that no other process can load the same object. If the load lock is busy the session will wait on this event until the lock becomes available.
Wait Time: 3 seconds (1 second for PMON)
Parameters:
object address |
Address of the object being loaded. |
lock address |
Address of load lock being used. |
mask |
Indicates which data pieces of the object that needs to be loaded. |
This event controls the concurrency between clients of the library cache. It acquires a lock on the object handle so that either:
This lock is also obtained to locate an object in the library cache.
Wait Time: 3 seconds (1 second for PMON)
Parameters:
This event manages library cache concurrency. Pinning an object causes the heaps to be loaded into memory. If a client wants to modify or examine the object, the client must acquire a pin after the lock.
Wait Time: 3 seconds (1 second for PMON)
Parameters:
The lock manager waits for a message from a remote lock manager in the same configuration.
Wait Time: The elapsed time of the wait
Parameter:
waittime |
The elapsed time of the actual wait. |
Waiting for space in the log buffer because the session is writing data into the log buffer faster than LGWR can write it out. Consider making the log buffer bigger if it is small, or moving the log files to faster disks such as striped disks.
Wait Time: Usually 1 second, but 5 seconds if it is waiting for a Switch Logfile to complete.
Parameters: none
Writing redo records to the redo log files from the log buffer.
Wait Time: Time it takes for the I/Os to complete. Even though redo records are written in parallel, the parallel write is not complete until the last I/O is on disk.
Parameters:
files |
Number of files to be written. |
blocks |
Number of blocks to be written. |
requests |
Number of I/O requests. |
Waiting for the read from this logfile to return. This is used to read redo records from the log file.
Wait Time: Time it takes to complete the physical I/O (read).
log# |
The relative sequence number of the logfiles within a log group (used only when dumping the logfiles). |
block# |
See "block#" on page A-7. |
blocks |
The number of blocks to read. |
Waiting for the write to this logfile to complete. This event is used while updating the header of the logfile. It is signaled when adding a log file member and when incrementing sequence numbers.
Wait Time: Time it takes for the physical I/O (write) to complete.
Parameters:
log# |
This is the number of the group/log to which the session is currently writing. |
block# |
See "block#" on page A-7. |
blocks |
The number of blocks to write. |
Waiting for a log switch because the log that the LGWR will be switching into has not been archived yet. Check the alert file to make sure that archiving has not stopped due to a failed archive write. To speed archiving, consider adding more archive processes or putting the archive files on striped disks.
Wait Time: 1 second
Parameters: none
Waiting for a log switch because the session cannot wrap into the next log. Wrapping cannot be performed because the checkpoint for that log has not completed.
Wait Time: 1 second
Parameters: none
Waiting for a log switch because the log is being cleared due to a CLEAR LOGFILE command or implicit clear logfile executed by recovery.
Wait Time: 1 second
Parameters: none
Waiting for a log switch to complete.
Wait Time: 1 second
Parameters: none
When a user session commits, the session's redo information needs to be flushed to the redo logfile. The user session will post the LGWR to write the log buffer to the redo log file. When the LGWR has finished writing, it will post the user session.
Wait Time: The wait time includes the writing of the log buffer and the post.
Parameter:
buffer# |
The number of the physical buffer in the redo log buffer that needs to be sync'ed |
Used as part of the ALTER SYSTEM ARCHIVE LOG CHANGE scn command. The session waits for the current log from all open threads to be archived.
Wait Time: Wait for up to 10 seconds.
Parameter:
thread# |
The thread number of the thread that is currently archiving its current log. |
Another session is fetching the SCN (System Change Number). This session waits for the other session finish fetching the SCN.
Wait Time: 1 second
Parameters: none
Used when creating or starting a Parallel Query Slave.
Wait Time: The time it takes to start all of the requested Parallel Query Slaves.
Parameters:
The process is waiting for a message during a parallel execute.
Wait Time: The wait time depends on how quickly the message arrives. Wait times can vary, but it will normally be a short period of time.
Parameters:
reason |
The reason for dequeuing. |
sleeptime |
The amount of time that the session slept. |
loop |
The total number of times that the session has slept. |
Each Parallel Query Process has a parallel query qref latch, which needs to be acquired before the queue buffers can be manipulated.
Wait Time: Wait up to 1 second.
During normal or immediate shutdown the Parallel Query Slaves are posted to shutdown cleanly. If any Parallel Query Slaves are still alive after 10 seconds, they are killed.
Wait Time: Wait up to 0.5 seconds.
Parameters:
This event occurs only in Exclusive mode. The Query Coordinator is signalling the Query Slaves that an error has occurred.
Wait Time: 0.5 seconds
Parameters:
serial |
The serial number of the slave process queue. |
error |
The error that has occurred. |
nbusy |
The number of slave processes that are still busy. |
The session is waiting for an outstanding AST to be delivered before the lock element can be used.
Wait Time: The session yields the CPU.
Parameter:
lenum |
See "lenum" on page A-8. |
This event should happen only during testing. The session waits for pending transactions to clear.
Wait Time: 30 seconds
Parameter:
scans |
Number of times the session has scanned the PENDING_TRANS$ table. |
The session waits for a message to be received on the pipe or for the pipe timer to expire.
Wait Time: There is a 5 second wake up (check) and the pipe timer set by the user.
Parameters:
handle address |
The library cache object handle for this pipe. |
buffer length |
The length of the buffer. |
timeout |
The pipe timer set by the user. |
The session waits for the pipe send timer to expire or for space to be made available in the pipe.
Wait Time: There is the 5 second wakeup (check) and the user-supplied timeout value.
handle address |
The library cache object handle for this pipe. |
record length |
The length of the record or buffer that has been put into the pipe. |
timeout |
The pipe timer set by the user. |
This is the main wait event for PMON. When PMON is idle, it is waiting on this event.
Wait Time: Up to 3 seconds, if not posted before.
Parameter:
duration |
The actual amount of time that the PMON is trying to sleep. |
Wait for a Multi-Threaded Server (Shared Server), Dispatcher, or other background process to start.
Wait Time: Wait up to 1 second for a background process to start. If timed out, then re-wait until 5 minutes have passed and signal an error. If the process has started, the event will acknowledge this.
Parameters:
type |
The process type that was started. |
process# |
The process number of the process being started. |
waited |
Cumulative time waited for the process to start. |
The session is waiting on an empty OLTP queue (Advanced Queue) for a message to arrive so that the session can dequeue that message.
Wait Time: The amount of time that the session wants to wait is determined by the parameter wait time.
Parameters:
queue id |
The ID of the OLTP queue for which this session is waiting. |
process# |
The process number of the process in which this session runs. |
wait time |
The intended wait time for this session. |
The direct loader uses a queue of slots for managing buffers. These slots are used for read/write operations. If a new slot is requested, but none are available, then this wait event is signaled. This wait will only occur if the underlying operating system is using asynchronous I/O.
Wait Time: Wait up to 1 second for slots to be freed in the circular direct loader I/O buffer queue.
Parameters: none
The background processes (LGWR, DBWR, LCK0) use this event to indicate that they are idle and are waiting for the foreground processes to send them an IPC message to do some work.
Wait Time: Up to 3 seconds. The parameter timeout shows the true sleep time.
Parameter:
timeout |
The amount of time that the session waits for an IPC message. |
This event indicates that all message blocks are in use and that the session had to wait for a message block to become available.
Wait Time: Wait up to 60 seconds.
Parameters: none
This event is used to wait for a reply from one of the background processes.
Wait Time: The wait time is specified by the user and is indicated by the parameter timeout.
Parameters:
Defined but not used by the code.
The session is trying to get a data dictionary lock.
Wait Time: Wait up to 60 seconds.
Parameters:
cache id |
The CACHE# column value in the V$ROWCACHE view. |
mode |
See "mode" on page A-8. |
request |
The pipe timer set by the user. |
Called by the session to find the highest lock mode that is held on a resource.
Wait Time: Wait up to 0.2 seconds, but the wait will continue until the NULL mode Acquisition AST has fired.
Parameters: none
When running single task, this event indicates that the session waits for the client side of the executable.
Wait Time: Total elapsed time that this session spent in the user application.
Parameters: none
This is the main idle event for SMON. SMON will be waiting on this event most of the time until it times out or is posted by another process.
Wait Time: 5 minutes (300 seconds)
Parameters:
sleeptime |
The amount of time that SMON tries to wait on this event in seconds. |
failed |
The number of times SMON was posted when there some kind of error. |
The session waits on the user command SWITCH LOGFILE to complete.
Wait Time: 5 seconds
Parameters: none
The session waits for the Archiver (ARCH) asynchronous I/O to complete.
Wait Time: 0.01 seconds
Parameters: none
Wait for a blocking transaction to be rolled back. Continue waiting until the transaction has been rolled back.
Wait Time: 1 second
Parameters:
The session waits to see if there are any transactions that have been started but do not have a Rollback Segment associated with them.
Wait Time: 1 second
Parameters: none
The undo segment is being extended or shrunk. The session must wait until the operation on the undo segment has finished.
Wait Time: 0.01 seconds
Parameter:
segment# |
The ID of the rollback segment that is being extended or shrunk. |
PMON is rolling back a dead transaction. The wait continues until rollback finishes.
Wait Time: 3 seconds
Parameters:
segment# |
The ID of the rollback segment that contains the transaction that is being rolled back. |
tx flags |
The transaction flags (options) set for the transaction that is being rolled back. |
Wait for a transaction slot to become available within the selected rollback segment. Continue waiting until the slot is available.
Wait Time: 1 second
Parameters:
segment# |
The ID of the rollback segment that contains the transaction that is being rolled back. |
The session waits for a virtual circuit to return a message type indicated by status.
Wait Time: 30 seconds
Parameters:
circuit# |
Indicates the virtual circuit# being waited on. |
status |
Indicates what the session is waiting for. |
The session waits for a buffer to be written. The write is caused by normal aging or by a cross-instance call.
Wait Time: 1 second
Parameters:
The session is blocked until the instance that started Instance Recovery is finished.
Wait Time: 5 seconds
Parameters:
bythread# |
The rollback segment id that contains the transaction that is being rolled back. |
ourthread# |
The current instance thread number. |