enq: TM - contention Wait Event , Cause, Related SQL queries, Possible Resolution

The "enq: TM - contention" wait event in Oracle indicates contention for a table-level lock. This contention occurs when multiple sessions are attempting to acquire conflicting table-level locks concurrently, leading to performance issues as sessions have to wait for the locks to be released before they can proceed with their operations. 

 While there are similarities in the resolution strategies for "enq: TX - index contention" and "enq: TM - contention," they do involve different types of contention (index-level vs. table-level). To clarify, here are specific resolution strategies for "enq: TM - contention" related to table-level lock contention: 

enq: TX - index contention Wait Event , Cause, Related SQL queries, Possible Resolution

The "enq: TX - index contention" wait event in Oracle occurs when multiple database sessions are contending for locks on the same index block. This contention can lead to performance issues as sessions have to wait for the locks to be released before they can proceed with their operations.

 Explanation: 

 In Oracle, locks are used to control access to data structures, including index blocks, to maintain data consistency and integrity. 

enq: TX - row lock contention Wait Event , Cause, Related SQL queries, Possible Resolution

The "enq: TX - row lock contention" wait event in Oracle occurs when multiple database sessions are contending for locks on the same row in a table. This contention can lead to performance issues, as sessions have to wait for the locks to be released before they can proceed with their operations.

 Explanation: In Oracle, locks are used to control access to data to maintain data consistency and integrity. 

Latch Free Wait Event , Cause, Related SQL queries, Possible Resolution

wait event in Oracle occurs when a session is trying to acquire a latch but finds it unavailable, resulting in a wait condition. Latches are low-level synchronization mechanisms used by Oracle to protect shared data structures in the SGA (System Global Area) from concurrent access. 

 Explanation: Latches are used to coordinate access to data structures like buffers in the buffer cache, library cache, or other shared memory structures. 

The "Latch Free" wait event happens when a session is waiting for a latch to become available. 

The wait event can occur for various reasons, including contention for a particular latch, inefficient latch acquisition patterns, or excessive latch acquisition requests. 

Log file sequential read Wait Event , Cause, Related SQL queries, Possible Resolution

The "log file sequential read" wait event occurs when a session is waiting for a single redo log file block to be read from disk into the buffer cache in a sequential manner. This wait event is common during log file access operations, such as reading redo log records during recovery or archive log processing. 

 Explanation: During database operations, especially during recovery processes, Oracle may need to read specific redo log records stored in redo log files on disk. 

The "log file sequential read" wait event indicates that a session is waiting for an I/O operation to complete, bringing the requested redo log block into the buffer cache.