Upgrading WebSphere® ESB for z/OS® is a multiphase process that can span multiple roles.
For additional information, refer to Applying product maintenance and file system configuration strategy.
In this scenario, you upgrade WebSphere ESB for z/OS by using SMP/E to load the newer version of the product separate from the existing installation file system (Figure 2).
You can then run the upgrade script for each application server that you want to upgrade. The upgrade process changes the service level symbolic link from the existing installation file system to the newer installation file system for the application server.
Subsequently, the applyPTF.sh script is run when the server controller starts. The script checks the level of the configuration file system against the level of the installation file system. In this case, the configuration file system is at a lower level than the installation file system, and the applyPTF.sh script performs the changes to the configuration file system specified by the maintenance level of the installation file system and starts the server.
In Figure 2, the newer version of the WebSphere ESB for z/OS has been installed and configured to run on application server A. To upgrade application server B, the systems programmer can run the upgrade script. The script updates the application server B Configuration file system by pointing its service level symbolic link to the new installation file system associated with application server A. The installation upgrade is completed when the applyPTF.sh script is run.
Using the upgrade script with intermediate symbolic links
This example is similar to scenario in Figure 2, except that rather than a direct symbolic link between the installation file system and configuration file system, an intermediate symbolic link is used. The intermediate symbolic link is a standard symbolic link that points to the installation file system and the configuration file system points to the intermediate symbolic link. Changing a node to another service level simply involves changing the single intermediate symbolic link.
You can run the upgrade script for each application server that you want to upgrade. The script uses the newer version of the installed file system to update the symbolic links for the configuration file system that you want to update. The configuration file system points to the intermediate symbolic link, which is an additional layer of indirection.