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.
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…
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.
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.
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…
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 Parameter Description rootdba The root…
This wait event can occur for several reasons. All buffer gets have been suspended. This could happen when a file was read-only and is now read/write. All the existing buffers must be invalidated since they are not linked to lock elements (needed when mounted parallel (shared)). So cache buffers are not assigned to data block…
This wait event can occur for several reasons. If one user is wanting to update or delete a row or rows that another session is modifying. The session holding the lock will release it when it performs a COMMIT or ROLLBACK. If a session is waiting due to potential duplicates in a UNIQUE index. If…
This event is used to wait for disk file operations (for example, open, close, seek, and resize). It is also used for miscellaneous I/O operations such as block dumps and password file accesses. Wait Time: The wait time is the actual time it takes to do the I/O Parameter Description FileOperation Type of file operation…
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…
Oracle Database Internal Mechanism 