You can tailor DFSMShsm ABARS functions with the DFSMShsm ABARS installation exits. As you write exits, remember that they run as if they were DFSMShsm code. Therefore, it is recommended that you routinely incorporate the following considerations whenever you write ABARS installation exits:

• Keep supervisor services such as I/O to a minimum.
• It is not necessary to write the ABARS installation exits as reentrant, with the exception of ARCTVEXT (ABARS tape volume exit).

Also always remember that DFSMShsm installation exits:

• Run enabled for interrupts.
• Run in problem program state.
• Run in either the DFSMShsm primary address space or the ABARS secondary address space.
• Have pageable storage.
• Are protected by ESTAE.
• Are entered in the standard address space protection key of 8. Control must return in the same key as at entry.
• Execute in an authorized program facility (APF) authorized address space.