This event occurs in the DBWR. It indicates the time that DBWR spends waiting for I/O completion. If asynchronous I/O is available, then the db file asynch I/O submit wait event captures any time spent in submitting I/Os to the underlying storage. When asynchronous I/O is not available, db file parallel write captures the time…
This happens during recovery. It can also happen during buffer prefetching, as an optimization (rather than performing multiple single-block reads). Database blocks that must be changed as part of recovery are read in parallel from the database. Wait Time: Wait until all of the I/Os are completed Parameter Description files This indicates the number of files…
When asynchronous I/O is available, this wait event captures any time spent in submitting I/Os to the underlying storage.
A session waits on this event when it is requesting an exclusive mutex pin for a cursor object and it must wait because the resource is busy. The mutex pin for a cursor object can be busy either because a session is already holding it exclusive, or there are one or more sessions which are holding…
This wait is signaled while the control file’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 Parameter Description file# This identifies the…
A session waits for this event when it is requesting a shared mutex pin and another session is holding an exclusive mutex pin on the same cursor object. Wait Time: Microseconds Parameter Description P1 Hash value of cursor P2 Mutex value (top 2 bytes contains SID holding mutex in exclusive mode, and bottom two bytes…
A session waits on this event when it wants to update a shared mutex pin and another session is currently in the process of updating a shared mutex pin for the same cursor object. This wait event should rarely be seen because a shared mutex pin update is very fast. Wait Time: Microseconds Parameter Description P1…
The session requests the mutex for a cursor object in exclusive mode, and it must wait because the resource is busy. The mutex is busy because either the mutex is being held in exclusive mode by another session or the mutex is being held shared by one or more sessions. The existing mutex holder(s) must release…
A session waits on this event when it is requesting a mutex in shared mode, when another session is currently holding a this mutex in exclusive mode on the same cursor object. Parameter Description P1 Hash value of cursor P2 Mutex value (top 2 bytes contain SID holding mutex in exclusive mode, and bottom two…
Reading from the control file. This happens often. For example, while: Making a backup of the control files Sharing information (between instances) from the control file Reading other blocks from the control files Reading the header block Wait Time: The wait time is the elapsed time of the read Parameter Description file# The control file from…
Oracle Database Internal Mechanism 