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In Oracle StateIconIn Oracle Sub-StateDescriptionTypical Oracle Events
Using CPUUsing CPUThe session is using CPU executing SQL.N/A
I/O Wait Direct I/O WaitThe session is waiting on direct I/O.direct path read; direct path write
I/O WaitScattered I/O WaitThe session is waiting on scattered I/O.db file scattered read
I/O Wait Sequential I/O Waitthe session is waiting on sequential I/O.db file sequential read; control file sequential read
I/O WaitOther I/O Waitthe session is waiting on another type of I/O.db file parallel write; log file parallel write; control file parallel write; asynch disk I/O
I/O Wait  
Info

The I/O sub-states Direct I/O Wait, Scattered I/O Wait, Sequential I/O Wait, and Other

I/O Wait only apply to Oracle files, objects, and storage entities. For other entities, the sub-state is simply shown as I/O Wait.

 
Application Lock Wait Row Lock Waitthe session is waiting on row locks. Enq: TX - row lock contention (Oracle 10g) 
Application Lock Wait  Table Lock WaitThe session is waiting on table locks.Enq: TM - contention (Oracle 10g)
Internal Lock WaitOther Lock WaitThe session is waiting on other Oracle locks, such as streams, latches, or internal locks.STREAMS events; enqueue; other enq: events; latch activity; latch free; latch: events
Application Lock Wait  
Info

Enqueue may appear in Row Lock Wait and Table Lock Wait, depending on the values of the P1, P2, and P3 parameters. The Collector captures these parameters and assigns the wait state accordingly. This can be seen in the Current and Activity tabs. However, the Collect Instance Statistics PMDB process does not capture the parameters so that in the Statistics tab, the wait is always shown as Other Lock Wait.   

 
Operating System WaitsCPU WaitThe session is in the operating system queue waiting for CPU.N/A
Operating System Waits Memory WaitThe session is waiting on a memory operation, such as page-in or page-out. This sub-state may also include memory-mapped I/O.N/A
Operating System WaitsOther Host WaitThe session is waiting on another type of OS operation, such as sorting.N/A
RAC/OPS/ Other Waits RAC/OPS WaitThe session is waiting on RAC or OPS synchronization.DFS events; DLM events; gc events; gcs events; ges events; global events
RAC/OPS/ Other WaitsOther WaitThe session is waiting on another, less common lock event.N/A
Commit & Checkpoint Waits Rollback Segment WaitThe session is waiting on a rollback segment operation.alter rbs offline; undo segment events
Commit & Checkpoint WaitsRedo Log Buffer WaitThe session is waiting on a redo log buffer operation.log buffer space; log file syn
Commit & Checkpoint Waits Log Switch and Clear WaitThe session is waiting for a log switch and clear operation to occur.checkpoint events; log file switch events
Oracle Server

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WaitImage Added

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Parallel Query Server Wait

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The session is waiting for a parallel query server to become available.

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PX create server; PX server shutdown; parallel query; create server; parallel query; dequeue wait
Oracle Server

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Wait Parallel Query Sync.

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WaitThe session is waiting for a parallel query server to get synchronized with another parallel query server.

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Other PX events; other parallel query events

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Oracle Server WaitImage AddedResource Manager WaitThe session is waiting for a resource to become available (only if the database resource manager is enabled).

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resmgr events
Oracle Server

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Wait Multi-Threaded Server Wait

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The session is waiting for a

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multi-threaded server to become available.

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alter system set dispatcher; alter system set mts_dispatcher
Oracle Server

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WaitImage Added

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Background Process Wait

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The session is waiting for an Oracle background process, such as DBWR or LGWR.

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LGWR events
Client Request

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Wait Request waitRequest wait is generally considered as an idle event as the Oracle server process is waiting for the client process.

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Client messages
Communication

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WaitImage Added

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Oracle/Oracle Communication Wait

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The session is waiting for another Oracle instance, usually as a result of a DBLINK event or a standby database.

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SQL*Net break/reset to DBLINK; SQL*Net message from DBLINK; SQL*Net message to DBLINK; SQL*Net more data from DBLINK; SQL*Net more

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data to DBLINK

Communication

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Wait 

Oracle/Client

Communication

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Wait

The session is waiting for data sent to the client, usually as a result of a selected statement, or for data sent from a client, usually as a result of bind variables.

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SQL*Net break/reset to client; SQL*Net message to client; SQL*Net more data from client; SQL*Net more data to client
Internal Lock

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Wait 

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Shared Pool

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WaitThe session is waiting for a shared pool operation.

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library cache load lock; library cache lock; library cache pin
Internal Lock

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Wait Buffer WaitThe session is waiting for a buffer cache operation.

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buffer busy; buffer busy wait;

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buffer latch

Anchor
IOwait
IOwait
I/O wait

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