Oracle RAC Session Module Waits Test
For each session module on a monitored instance, this test reports the number and nature of wait events that occurred during the last measurement period. In addition, the test also reports the total number of events (of a type) that occurred across all modules and instances. With the help of these metrics, administrators can figure out how much time an instance has spent waiting and what it was waiting for; a high value is a cause for concern, as it indicates that the instance has waited too long, and could have consequently suffered significant processing delays.
This test is disabled by default. To enable the test, go to the enable / disable tests page using the menu sequence : Agents -> Tests -> Enable/Disable, pick the Oracle RAC as desired Component type, set Performance as the Test type, choose the test from the disabled tests list, and click on the >> button to move the test to the ENABLED TESTS list. Finally, click the Update button.
Target of the test : Oracle RAC
Agent deploying the test : An internal/remote agent
Outputs of the test : One set of results for every session module on each instance of the monitored Oracle RAC.
|
Measurement | Description | Measurement Unit | Interpretation |
---|---|---|---|
Cpu waits: |
Indicates the number of times since the last measurement period this session module on this instance has waited for CPU. |
Number |
Ideally, the value of this measure should be low. |
User IO waits: |
Indicates the total number of waits that have occurred in this session module on this instance for user I/O, since the last measurement period. |
Number |
Some of the user I/O wait events include: BFILE read, buffer read retry, db file parallel read, db file scattered read, db file sequential read, and db file single write. Ideally, the value of this measure should be low. |
Cluster waits: |
Indicates the total number of waits pertaining to cluster resources that have occurred in this session module on this instance since the last measurement period. |
Number |
A low value is desired for this measure. |
Committed waits: |
Indicates the total number of commit waits that have occurred in this session module on this instance since the last measurement period. |
Number |
A low value is desired for this measure. If this measure shows a high value, refer to the detailed diagnosis capability of this measure to identify the sessions that are affected by committed waits. |
Transaction lock waits: |
Indicates the number of times this session module on this instance waited for transaction locks, during the last measurement period. |
Number |
A low value is desired for this measure. If this measure shows a high value, use the detailed diagnosis of the RAC Transaction Locks test to obtain the detailed report on all the sessions that are affected by the lock waits. |
Latch waits: |
Indicates the total number of latch waits that have occurred in this session module since the last measurement period. |
Number |
A low value is desired for this measure. |
Other waits: |
Indicates the total number of times since the last measurement period waits that should typically not occur on a system (eg., ‘wait for EMON to spawn’) occurred in this session module on this instance. |
Number |
Ideally, the value of this measure should be low. |