Oracle RAC Session Waits Test
This test reports the number and nature of session wait events that occurred on each instance of the monitored RAC during the last measurement period. In addition, the test also reports the total number of events (of a type) that occurred across all 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 slowdowns.
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 Cluster as the 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 each instance of the monitored Oracle RAC.
|
Measurement | Description | Measurement Unit | Interpretation |
---|---|---|---|
Cpu waits: |
Indicates the number of times since the last measurement period the sessions on this instance waited for CPU. |
Number |
Ideally, the value of this measure should be low. |
IO waits: |
Indicates the total number of times the sessions on this instance waited 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 times the sessions on this instance waited for cluster resources 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 the sessions of 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 the sessions 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 the sessions of this instance since the last measurement period. |
Number |
A low value is desired for this measure. |
Configuration waits: |
Indicates the total number of configuration wait events that occurred in the sessions of this instance during the last measurement period. |
Number |
Configuration waits are waits caused by inadequate configuration of database or instance resources (for example, undersized log file sizes, shared pool size). Ideally, the value of this measure should be low. |
System IO waits: |
Indicates the total number of system I/O wait events that occurred in the sessions of this instance during the last measurement period. |
Number |
System I/O waits are waits for background process I/O (for example, DBWR wait for ‘db file parallel write’). Ideally, the value of this measure should be low. |
Network waits: |
Indicates the total number of times since the last measurement period waits related to network messaging (for example, ‘SQL*Net more data to dblink’, occurred in the sessions of this instance. |
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 the sessions of this instance. |
Number |
Ideally, the value of this measure should be low. |
Subtotal waits: |
Indicates the overall number of waits that have occurred since the last measurement period in the sessions of this Oracle instance. |
Number |
Ideally, the value of this measure should be low. |