Determining How Many Files to Define

All the side information used by a system must be contained in one file that is named in the SIDEINFO statement of an APPCPMxx parmlib member. TP profiles, however, can be contained in either a single file or in many files. Files for side information and TP profiles can be shared by more than one system. Using a global resource serialization star or ring complex is one method of allowing systems to safely share these files. See z/OS DFSMS Using Data Sets for more information about sharing VSAM data sets among systems.

The number of files you need to define for profiles is related to the number of local LUs in MVS. You can name one TP profile file for each local LU when the LU is created. You can name a different file for each LU, or name the same file for several or all LUs. For example, in Figure 1, File-1 is the TP profile file for several LUs, namely LU-A, LU-B, and LU-C. File-2 is the exclusive TP profile file for LU-D.

Figure 1. Relationship of files to LUs

                LU-A  }
                LU-B  }         File-1
                LU-C  }


                LU-D  }         File-2

Whether you need many TP profile files or only one might depend on:

Isolation: Although access to the individual TP profiles in a file can be controlled by level (system, group, and user), an installation might choose to isolate the communication that passes through a single LU. If so, the LU might need an exclusive TP profile file.
Scheduling: An LU is associated with a single transaction scheduler, and the TP profile file for that LU should contain profiles for TPs scheduled by that transaction scheduler. In the previous figure, if LU-A, LU-B, and LU-C are associated with the APPC/MVS transaction scheduler, and LU-D is associated with transaction scheduler XYZ, File-1 should contain profiles for TPs scheduled by the APPC/MVS transaction scheduler and File-2 should contain profiles for TPs scheduled by XYZ.
Testing: An installation might choose to devote an LU to pre-production testing and associate it with a separate TP profile file that contains only profiles for TPs to be tested.
Delegation of administrative responsibilities: Files can be associated with departments or groups within an installation and maintained by different administrators.
Sharing files on more than one system: When systems share files, the files cannot be updated when in use. Therefore, you might want to create two rotating copies of each file, one to use and the other to update. For more information, see Restrictions on Invoking the APPC/MVS Administration Utility.

Basically, many files allow flexibility, but a single file is easier to administer. Carefully consider whether the multiple files you need for flexibility outweigh the efficiency of keeping all TP profiles together in one file.