When migrating to a new release, verify that all necessary files and directories have been created in each /var directory in each file system on all system images. If you use the /var directories and the provided symbolic links, you do not need to customize the cron, uucp, and mail utilities in order for the root file system to be mounted in read-only mode.

However, if you decide not to use the /var directory and the provided symbolic links, you can create symbolic links from the /var directory or file to your preferred directory or file. With that setup, each time you migrate to a new release, you will have to customize the z/OS Migration in order for the root file system to be mounted read-only.