Wait Event – rdbms ipc reply

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.   Parameter Description from_process The background process for which the session is waiting. The wait is for a reply to an IPC message sent by…

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 – 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 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…

Wait Event – free buffer waits

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…

Wait Event – enq: TX – row lock contention

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…

Wait Event – Disk file operations I/O

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…

Wait Event – DFS lock handle

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…