Application placement policies

Application placement policies

A resource can be started on any server, subject to the placement policies, the resource start dependencies, and the availability of the action script on that server.

The PLACEMENT resource attribute determines how Oracle Clusterware selects a server on which to start a resource and where to relocate the resource after a server failure.

The HOSTING_MEMBERS and SERVER_POOLS attributes determine eligible servers to host a resource and the PLACEMENT attribute further refines the placement of resources.

The value of the PLACEMENT resource attribute determines how Oracle Clusterware places resources when they are added to the cluster or when a server fails. Together with either the HOSTING_MEMBERS or SERVER_POOLS attributes, you can configure how Oracle Clusterware places the resources in a cluster. When the value of the PLACEMENT attribute is:

·         balanced: Oracle Clusterware uses any online server for placement. Less loaded servers are preferred to servers with greater loads. To measure how loaded a server is, Oracle Clusterware uses the LOAD resource attribute of the resources that are in an ONLINE state on the server. Oracle Clusterware uses the sum total of the LOAD values to measure the current server load.

·         favored: If values are assigned to either the SERVER_POOLS or HOSTING_MEMBERS resource attribute, then Oracle Clusterware considers servers belonging to the member list in either attribute first. If no servers are available, then Oracle Clusterware places the resource on any other available server. If there are values for both the SERVER_POOLS and HOSTING_MEMBERS attributes, then the SERVER_POOLS attribute restricts the choices to the servers within the preference indicated by the value of HOSTING_MEMBERS.

·         restricted: Oracle Clusterware only considers servers that belong to server pools listed in the SEVER_POOLS resource attribute or servers listed in the HOSTING_MEMBERS resource attribute for resource placement. Only one of these resource attributes can have a value, otherwise it results in an error.

Unregistering Applications and Application Resources

To unregister a resource, use the crsctl delete resource command. You cannot unregister an application or resource that is ONLINE or required by another resource, unless you use the -force option. The following example unregisters the Apache Web server application:

$ crsctl delete resource myApache

Run the crsctl delete resource command as a clean-up step when a resource is no longer managed by Oracle Clusterware. Oracle recommends that you unregister any unnecessary resources.