Dialog functions that are coded as CLIST or REXX command procedures can be in a procedure library that has been allocated to ddname SYSPROC before starting ISPF. A REXX command procedure can also be allocated to the SYSEXEC ddname. The SYSEXEC ddname is described in z/OS TSO/E REXX User's Guide.
You must link-edit dialog functions that have been coded as programs. The load module can reside in a step library, a system link library (such as SYS1.LINKLIB), or the link pack area. Alternatively, it can be in a partitioned data set (RECFM=U) allocated to ddname ISPLLIB(DISP=SHR). This library (the ISPF Link Library) can be used for testing new dialogs that contain program-coded functions. If used, it must be allocated prior to starting ISPF. ISPLLIB can specify a concatenated sequence of partitioned data sets.
ISPLLIB is used as a task library when fetching load modules. It is searched before the system link libraries and the link pack area. If ISPF product modules are kept in a step library and a task library (ISPLLIB) is used, the data sets containing the ISPF product modules should be included in the ISPLLIB concatenation sequence as well as the step library concatenation. If a program is to be used in split-screen mode it should be linked as reentrant or nonreusable.
If you are using the ISPF client/server (ISPF C/S) feature or the z/OS® UNIX Directory List Utility, the Language Environment® run-time library data sets SCEERUN and SCEERUN2 must be in STEPLIB or LNKLST. The modules in these data sets are not searched for in ISPLLIB.