Classes of Oracle Wait Events

Every oracle wait event belongs to a class of wait event. Here is the list of classes of oracle wait events.
1)Administrative: DBA commands cause users to wait. Example: index rebuild

2)Application: User application codes cause to wait. Example: row level lock

3)Cluster: Waits related to Real Application Cluster resources. Example: gc cr block busy

4)Commit: After issuing commit wait for redo log write confirmation. Example: log file sync

5)Concurrency: Waits for internal database resources. Example: Latch wait.

6)Configuration: Waits caused by inadequate configuration of database or instance resources Example: Undersized log file size, undersized shared pool size.

7)Idle: Waits that signify the session is inactive, that is session waiting for work. Example: SQL*Net message from client.

8)Network: Waits related to network messaging. Example: SQL*Net more data to dblink.

9)Other: Waits which should not typically occur on a system. Example:wait for EMON to spawn.

10)Scheduler: Resource Manager related waits. Example: resmgr: become active.

11)System I/O: Waits for background process IO. Example: DBWR waits for 'db file parallel write'.

12)User I/O: Waits for user IO. Example: 'db file sequential read'

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