The average wait time and the total wait time should be considered when being alerted to performance issues where these particular waits have a high impact. The gc current block busy wait event indicates that the access to cached data blocks was delayed because they were busy either in the remote or the local cache. The gc current block busy and gc cr block busy wait events indicate that the local instance that is making the request did not immediately receive a current or consistent read block. Oracle has been self-managing for a long time. Each instance has a set of instance-specific views, which are prefixed with V$. we will primarily look at the Global Cache waits. gc current block congested gc cr block congested: Enqueue Chart for Global Cache Block Access Latency: Each cluster database instance has its own buffer cache in its System Global Area (SGA). ------------, gcs messages You must have SYSDBA privileges to run this script. The length of time that Oracle Database needs to process the queue depends on the remaining service time for the block. frequently the root cause of the below wait events. A buffer may also be busy locally when a session has already initiated a cache fusion operation and is waiting for its completion when another session on the same node is trying to read or modify the same data. reading information from the buffer, reading and writing data to and from the be) required to get that block from the remote cache, recorded as the Focus on the buffer cache and its operations. Any session that is connected to the database and using CPU is considered an active session. the same instance has already requested the block. thus modifying the block. All legitimate Oracle experts In a RAC environment, the buffer cache is global across all instances in the cluster and hence the processing differs. In addition to the V$ information, each GV$ view contains an extra column named INST_ID of data type NUMBER. This section describes how to monitor GCS performance by identifying objects read and modified frequently and the service times imposed by the remote access. Wanted! The cache fusion protocol does not require I/O to data files in order to guarantee cache coherency and Oracle RAC inherently does not cause any more I/O to disk than a nonclustered instance. New Businesses. and system statistics. ASH report statistics provide details about Oracle Database session activity.