Operation of the Oracle Server Fault Monitor

The fault monitor for the Oracle server uses a request to the server to query the health of the server.

The server fault monitor is started through pmfadm to make the monitor highly available. If the monitor is killed for any reason, the Process Monitor Facility (PMF) automatically restarts the monitor.

The server fault monitor consists of the following processes.

• A main fault monitor process

• A database client fault probe

Operation of the Main Fault Monitor

The main fault monitor determines that an operation is successful if the database is online and no errors are returned during the transaction.

Operation of the Database Client Fault Probe

The database client fault probe performs the following operations:

1. Monitoring the partition for archived redo logs

2. If the partition is healthy, determining whether the database is operational

The probe uses the timeout value that is set in the resource property Probe_timeout to determine how much time to allocate to successfully probe Oracle.

Operations to Monitor the Partition for Archived Redo Logs

The database client fault probe queries the dynamic performance view v$archive_dest to determine all possible destinations for archived redo logs. For every active destination, the probe determines whether the destination is healthy and has sufficient free space for storing archived redo logs.

• If the destination is healthy, the probe determines the amount of free space in the destination's file system. If the amount of free space is less than 10% of the file system's capacity and is less than 20 Mbytes, the probe prints a message to syslog.

• If the destination is in ERROR status, the probe prints a message to syslog and disables operations to determine whether the database is operational. The operations remain disabled until the error condition is cleared .

Operations to Determine Whether the Database is Operational

If the partition for archived redo logs is healthy, the database client fault probe queries the dynamic performance view v$sysstat to obtain database performance statistics. Changes to these statistics indicate that the database is operational. If these statistics remain unchanged between consecutive queries, the fault probe performs database transactions to determine if the database is operational. These transactions involve the creation, updating, and dropping of a table in the user table space.

The database client fault probe performs all its transactions as the Oracle user. The ID of this user is specified during the preparation of the nodes or zones as explained in How to Prepare the Nodes.

Actions by the Server Fault Monitor in Response to a Database Transaction Failure

If a database transaction fails, the server fault monitor performs an action that is determined by the error that caused the failure. To change the action that the server fault monitor performs, customize the server fault monitor as explained in Customizing the Sun Cluster HA for Oracle Server Fault Monitor.

If the action requires an external program to be run, the program is run as a separate process in the background.

Possible actions are as follows:

• Ignore. The server fault monitor ignores the error.

• Stop monitoring. The server fault monitor is stopped without shutting down the database.

• Restart. The server fault monitor stops and restarts the entity that is specified by the value of the Restart_type extension property:

  • If the Restart_type extension property is set to RESOURCE_RESTART, the server fault monitor restarts the database server resource. By default, the server fault monitor restarts the database server resource.

  • If the Restart_type extension property is set to RESOURCE_GROUP_RESTART, the server fault monitor restarts the database server resource group.

  ---

  Note –

  The number of attempts to restart might exceed the value of the Retry_count resource property within the time that the Retry_interval resource property specifies. If this situation occurs, the server fault monitor attempts to switch over the resource group to another node or zone.

  ---

• Switch over. The server fault monitor switches over the database server resource group to another node or zone. If no nodes or zones are available, the attempt to switch over the resource group fails. If the attempt to switch over the resource group fails, the database server is restarted.

Scanning of Logged Alerts by the Server Fault Monitor

The Oracle software logs alerts in an alert log file. The absolute path of this file is specified by the alert_log_file extension property of the SUNW.oracle_server resource. The server fault monitor scans the alert log file for new alerts at the following times:

• When the server fault monitor is started

• Each time that the server fault monitor queries the health of the server

If an action is defined for a logged alert that the server fault monitor detects, the server fault monitor performs the action in response to the alert.

Preset actions for logged alerts are listed in Table 2. To change the action that the server fault monitor performs, customize the server fault monitor as explained in Customizing the Sun Cluster HA for Oracle Server Fault Monitor.