Thursday, March 6, 2014

Defining Resource Dependencies

Defining Resource Dependencies

Click Dependencies to configure start and stop dependencies between resources for the new resource type. Two or more resources are dependent when they either depend on each other or affect other resources. For example, when Clusterware attempts to start a resource, it is necessary for any resources on which the initial resource depends to be online and in the same location. If Oracle Clusterware cannot bring the resources online, the initial (dependent) resource cannot be brought online either. Resource dependencies are separated into start and stop categories. This separation improves and expands the start and stop dependencies between resources and resource types.

Oracle Clusterware considers start dependencies between resources whenever a resource state changes from OFFLINE to ONLINE. Start dependencies displayed in EM include:

  • Hard: This defines a hard start dependency for a resource if another resource must be ONLINE before the dependent resource can start.
  • Weak: This means that an attempt is made to start the resource on which the resource in question is dependent on if it is not ONLINE.
  • Attraction: This indicates that Clusterware will attempt to start a resource on the same node on which the resource it is dependent on is running.Pullup: When you specify the pullup start dependency for a resource, this resource starts as a result of starting the named resources.
  • Dispersion: This indicates that the resource will not be located on the same server as dependent resources, if possible.
  • Stop Dependencies
Oracle Clusterware considers stop dependencies between resources whenever a resource state changes from ONLINE to OFFLINE.

Hard means that if a resource has a hard stop dependency on another resource, then the dependent resource must be stopped when the second transitions into the INTERMEDIATE, OFFLINE, or UNKNOWN state. The two resources may attempt to start or relocate to another server, depending upon how they are configured.

Clicking the flashlight icon to the right of the “Dependent On Resource” field brings up a list of registered resources to select from. When you have finished, return to the General folder tab and click the Submit button.

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