Wait Event – rdbms ipc message

The background processes (LGWR, DBWR, LMS0) 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 Description timeout The amount of time that the session waits…

Wait Event – log file parallel write

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.   Parameter Description files Number of files to be written blocks Number of…

Wait Event – log buffer space

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 Event – Log archive I/O

Used local archiving of online redo logs (for a production database) or standby redo logs (for a standby database). When the archiving process exhausts its I/O buffers because all of them are being used for on-going I/O’s, the wait for an available I/O buffer is captured in this system wait event.

Wait Event – library cache: mutex X

Library cache mutexes protect hash buckets within the shared pool. Each hash bucket contains a number of cursors. The mutex must be held in exclusive mode before any of the structures that it protects can be changed. This wait event is often associated with high parse activity.

Wait Event – library cache load lock

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…

Wait Event – latch: row cache objects

This event occurs when another session is modifying the contents of part of the dictionary cache (or row cache). This event is often associated with high parse activity but may occur for other reasons, such as manipulation of rollback segments. V$ROWCACHE may indicate which part of the row cache is being contended.

Wait Event – latch: redo copy

Redo copy latches are acquired by sessions in order to write changes into the redo log buffer and by the LGWR process to ensure that there are no current writers before it copies data from the buffer to the redo log.

Wait Event – latch free

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…