Sun Cluster 3.1 Data Services Developer's Guide

Method Code Change

If the method code is the only change in the updated resource type, it is important to determine whether the new method code is compatible with the previous version. This determines whether the new method code must be stored in a new pathname or whether the old methods can be overwritten.

If the new Stop, Postnet_stop and Fini methods (if declared) can be applied to resources that were initialized or started by the old versions of the Start, Prenet_stop, or Init methods, then it is possible to overwrite the old methods with the new methods.

If the new method code is not compatible with the previous version, then it is necessary to stop or unconfigure a resource using the old versions of the methods before it can be migrated to the upgraded resource type. If the new methods overwrite the old ones, it can require shutting down (and possibly unmanaging) all resources of the type before doing the resource type upgrade. If the new methods are stored separately from the old (and both are accessible at once), then even without backward compatibility it is possible to install the new resource type version and upgrade the resources one by one.

Even if the new methods are backward compatible, it might be a requirement to upgrade one resource at a time to use the new methods, while other resources continue to use the old methods. It still is necessary to store the new methods in a separate directory rather than overwriting the old ones.

An advantage to storing each resource type version's methods in a separate directory is that it makes it easy to switch resources back to the older resource type version if a problem arises with the newer version.

One packaging approach is to include all of the earlier versions that are still supported in the package. This permits the new package version to replace the older version, without overwriting or deleting the old method paths. It is up to the resource type developer to decide how many previous versions to support.

Note –

It is not recommended to overwrite methods or pkgrm/pkgadd methods on a node that is currently in the cluster. If the RGM were to call a method when the method is not accessible on disk, unexpected results can occur. Removing or replacing the binary of a running method might also cause unexpected results.