eG Monitoring
 

Measures reported by OraClstrIntrConTest

A cluster database comprises two or more nodes that are linked by an interconnect. The interconnect serves as the communication path between the nodes in the cluster database. Each Oracle instance uses the interconnect for the messaging that synchronizes each instance's use of shared resources. Oracle also uses the interconnect to transmit data blocks that the multiple instances share.

The non-availability of the interconnect can impair node-to-node communication in a cluster, thus bringing all critical cluster operations - like fail-over and load balancing - to a halt. With the cluster service not running, all mission-critical business services that overlay the clustered database will experience prolonged outages, resulting in considerable loss of revenue and reputation.

To avoid this, you need to continuously monitor the availability of the cluster interconnect, proactively detect availability issues, and promptly fix them. For this purpose, you can use the OraClstrIntrConTest. This test periodically verifies whether the nodes in the cluster are able to communicate via the cluster interconnect, and promptly reports the non-availability of the interconnect.

This test periodically verifies whether the nodes in the cluster are able to communicate via the cluster interconnect, and promptly reports the non-availability of the interconnect.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Intrcon_prcnt Indicates whether the cluster interconnect is available or not. Percent The value 0 for this measure indicates that the nodes in the cluster are unable to communicate via the cluster interconnect. The value 100 indicates that the interconnect is available and is enabling the nodes to communicate with each other.
Cum_logon_count Indicates the rate at which user logons occurred on this node. Logons/Sec  
Processes_utilization Indicates the number of processes currently running on this cluster node. Number As long as the value of this measure is much lower than the value of the PROCESSES setting in the database parameter file, the node will be able to handle the process load.
Session_utilization Indicates the number of sessions that are currently active on this node. Number As long as the value of this measure is much lower than the value of the SESSIONS setting in the database parameter file, the node will be able to handle the session load. If the value of this measure is unusually high for any cluster node, then compare the value of this measure across nodes to figure out whether/not load is uniformly distributed across all cluster nodes. If session load on most of the cluster nodes is high, then the sudden increase in session load could be attributed to an unavailable cluster interconnect. Because of the unavailability, the cluster service may not have been unable to contact the affected cluster node and may have been compelled to distribute the load amongst the remaining cluster nodes. This may have caused load on the other nodes to suddenly increase. To confirm this, check the value of the Intrcon_prcnt percentage measure of all nodes.

On the other hand, if no interconnect is unavailable, and if Session_utilization is abnormally high on a particular node only, it could mean that that node is indeed overloaded.
Pct_process_utilization Of the maximum number of processes this node can handle, what percentage is currently active on this cluster node. Percent Ideally, the value of this measure should be low. If this measure value is close to 100%, it could mean that the node is about to exhaust its processing limit and may not be able to handle any more processes. On the other hand, if the value of this measure is consistently high for a cluster node, then check the PROCESSES setting in the database parameter file to figure out whether/not the node has been configured with adequate processing capability. If this check reveals that the node has been configured with a limited number of processes than it can handle, you may want to increase the PROCESSES setting to suit the node's capacity.
Pct_session_utilization Of the maximum number of sessions this node can handle, what percentage is currently active on this cluster node. Percent Ideally, the value of this measure should be low. If this measure value is close to 100%, it could mean that the node may not be able to handle any more sessions. On the other hand, if the value of this measure is consistently high for a cluster node, then check the SESSIONS setting in the database parameter file to figure out whether/not the node has been configured with adequate session-handling capability. If this check reveals that the node has been configured with a limited number of sessions than it can handle, you may want to increase the SESSIONS setting to suit the node's true capacity.