A file can be exempted from migration in the following ways:
File attribute “MIGRATE”: the migration inhibit is set via MIGRATE=*INHIBITED of CREATE-FILE or MODIFY-FILE-ATTRIBUTES commands (canceled with MIGRATE=*ALLOWED).
This protection can be disabled by the system administrator, i.e. the file is only protected against “standard” migration. This attribute should therefore be used sparingly so that migration of non-protected files can relieve the load on disk storage and the system administrator is not forced to migrate protected files.User IDs that have the right to make physical allocations also have the MIGRATE=*FORBIDDEN option. This inhibits migration completely.
The system administrator can keep a list of important files that are to be protected. This list may also include user files. In addition to setting the file attribute MIGRATE=*FORBIDDEN, only the entry in this list protects the file concerned from migration.
All files that are open when the migration request is processed are likewise exempted from migration. However, this can normally be avoided by processing the migration request outside the standard session times.