ISPF LIBDEF Service

You can use the ISPF LIBDEF service to access IPCS messages, panels, and data set-tailoring skeletons. The use of LIBDEF is not required. However, effective use of LIBDEF can improve the performance of your IPCS dialogs. You should consider the following points about using LIBDEF:

Performance gains depend on the activities that the installation's IPCS users do most often.
- LIBDEF improves performance when:
  - Users logon to TSO/E; four fewer allocations take place.
  - Users run dialogs other than the IPCS dialog; fewer libraries are searched.
- LIBDEF slows performance when:
  - Users enter the IPCS dialog; ISPF dynamically allocates four libraries and opens them.
  - Users leave the IPCS dialog; ISPF closes and frees the four libraries.
If users enter and leave the IPCS dialog frequently, the use of LIBDEF might slow performance.
LIBDEF cannot be used to access IPCS program libraries concatenated to the ISPLLIB data set.

The BLSCLIBD CLIST and the BLSGLIBD dialog program both use the LIBDEF service.

See z/OS ISPF Dialog Tag Language Guide and Reference for more information on the LIBDEF service.