Wait Events的分類及分類依據

To enable easier high-level analysis of the wait events, the events are grouped into
classes. The wait event classes include: Administrative, Application, Cluster, Commit,
Concurrency, Configuration, Idle, Network, Other, Scheduler, System I/O, and User
I/O.

The wait classes are based on a common solution that usually applies to fixing a
problem with the wait event. For example, exclusive TX locks are generally an
application level issue and HW locks are generally a configuration issue.
The following list includes common examples of the waits in some of the classes:
■ Application: locks waits caused by row level locking or explicit lock commands
■ Commit: waits for redo log write confirmation after a commit
■ Idle: wait events that signify the session is inactive, such as SQL*Net message
from client
■ Network: waits for data to be sent over the network
■ User I/O: wait for blocks to be read off a disk

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