Oracle RAC Wait Event

PCM resource-related wait events

GC CURRENT/CR block Request: This wait event indicates that the application instance is requesting a current block or CR block, but the resource Master instance's LMS process has not responded to its request.

GC CURRENT/CR Block 2 way: This wait event indicates that the application instance has requested a current block or CR block from a remote instance through a 2-channel communication.

GC CURRENT/CR Block 3 way: This wait event indicates that the application instance has requested a current block or CR block from a remote instance through a 3-channel communication.

GC CURRENT/CR block busy: This wait event indicates that the application instance has requested a current block or CR block from the remote instance, and the remote instance has discovered that it is being used by another process when it sends the data block.

GC CURRENT/CR Grant 2-way: This wait event indicates that the application instance has requested a current block or CR block from the resource master instance, and that the request has been responded to by the resource master instance.

The difference between GC CURRENT/CR Grant 2-way and GC CURRENT/CR block 2/3-way is that the requested data block is not contained in the buffer cache of any instance and needs to be read from the data file by the instance itself. So there is no waiting event for GC CURRENT/CR Grant 3-way exists because there are only resource requisition instances and resource master instances, and there are no resources to hold instances. In GC CURRENT/CR block 2/3-way, the data block obtained by the application instance is sent by the remote instance, the application instance, the master instance and the holding instance may be 3 different instances. After the GC CURRENT/CR Grant 2-way appears, the next step is to read the data from the data file, which is why GC CURRENT/CR grant 2-way with DB file sequential read or db file scattered The reason that the read wait event occurs at the same time.

GC Current GRANT busy: This wait event indicates that the application instance has requested an existing block, and the resource master instance has confirmed that the application instance can hold the data block, but the requester is waiting for other applicants to complete their request. This wait event indicates that the applicant has applied for the data block in an exclusive manner, but there are other instances on the other instance that are requesting this fast in a shared manner, so an exclusive request for an application waits for a share request that arrives before it. The grant busy only appears on the current block, corresponding to the CR block, because the process cannot modify data already in a CR block, so there is no wait event GC CR Grant busy

GC CURRENT/CR block congested: This wait event indicates that the application instance has requested a current block or CR block from the remote instance, and the remote instance has received the request, but the LMS process does not respond to the request--the data block is sent to the application instance.

GC CURRENT/CR Grant congested: This wait event indicates that the application instance has requested a current block or CR block from the remote instance, and the remote instance has received the request, but the LMS process did not respond to the request-sending the feedback to the application instance.

GC CR FAILURE/GC Current Retry: This wait event indicates that the application instance did not receive a present block or a CR block.

GC CURRENT/CR Multi block Request: This wait-time event request instance requires multiple current blocks or CR blocks to be requested from the remote instance.

This wait time will not end until all the requested databases have been successfully returned, and if one of the databases has not been successfully received for some reason, it will need to re-apply all data blocks. This is why GC CURRENT/CR multi block request is often and waits for the event GC CR FAILURE/GC Current retry to occur simultaneously.

Oracle RAC Wait Event