This event occurs when a session requests a buffer that is currently being read into the buffer cache by another session. Prior to release 10.1, waits for this event were grouped with the other reasons for waiting for buffers under the ‘buffer busy waits’ event. Wait Time: Time waited for the buffer to be read by the…
When asynchronous I/O is available, this wait event captures any time spent in submitting I/Os to the underlying storage.
The session requests the mutex for a cursor object in exclusive mode, and it must wait because the resource is busy. The mutex is busy because either the mutex is being held in exclusive mode by another session or the mutex is being held shared by one or more sessions. The existing mutex holder(s) must release…
A session waits on this event when it is requesting a mutex in shared mode, when another session is currently holding a this mutex in exclusive mode on the same cursor object. Parameter Description P1 Hash value of cursor P2 Mutex value (top 2 bytes contain SID holding mutex in exclusive mode, and bottom two…
When a process spawn is aborted while the process spawning background is in the middle of spawning, the current session must wait until the pid of the new process is filled in. Once the pid is filled in, then the process spawn can be actually aborted.
A session waits for a checkpoint to complete. This could happen, for example, during a close database or a local checkpoint.
This event occurs only if the instance is mounted in shared mode (Oracle Real Application Cluster). During the read of the buffer, the contents changed. This means that either: The version number, dba, or the incarnation and sequence number stored in the block no longer match The checksum on the block does not match the…
The session waits on the buffer hash chain latch. Primarily used in the dump routines. The virtual address in the SGA where this latch is located. Use the following statement to find the name of this latch: select * from v$latch a, v$latchname b where addr = latch addr and a.latch# = b.latch#; chain# The…
Oracle does not really wait on this event; the foreground only yields the CPU. Thus, the chances of catching this event are very low. This is not an application induced deadlock, but an assumed deadlock by the cache layer. The cache layer cannot get a buffer in a certain mode within a certain amount of…
A session has issued a statement ALTER SYSTEM SET DISPATCHER = string and is waiting for the dispatchers to get started. Wait Time: The session will wait 1 / 100 of a second and verify if the new dispatchers have started, else the session will wait again
Oracle Database Internal Mechanism 