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…
This event occurs only for the DBWR in Real Application Clusters. 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…
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 Parameter Description file# See “file#” block# See “block#” blocks This is the number of blocks that the session is trying to write in file# starting at block#
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…
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…
Oracle Database Internal Mechanism 