Performance Views in Oracle RAC

Each instance has a set of instance-specific views, which are prefixed with V$. You can also query global dynamic performance views to retrieve performance information from all of the qualified instances. Global dynamic performance view names are prefixed with GV$.

Querying a GV$ view retrieves the V$ view information from all qualified instances. In addition to the V$ information, each GV$ view contains an extra column named INST_ID of data type NUMBER. The INST_ID column displays the instance number from which the associated V$ view information was obtained.

You can use the INST_ID column as a filter to retrieve V$ information from a subset of available instances. For example, the following query retrieves the information from the V$LOCK view for instances 2 and 5:

SQL> SELECT * FROM GV$LOCK WHERE INST_ID = 2 OR INST_ID = 5;