PREDECESSOR/SUCCESSOR LIMITS. MESSAGES EQQ0370W and EQQ0522I

Answer

In TWSz, no APPLICATION can ever be a PREDECESSOR of more than 1000 other applications. To state this another way, no APPLICATION OCCURRENCE in the CURRENT PLAN can have EXTERNAL SUCCESSORS in more than 1000 DIFFERENT APPLICATIONS.
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When any application is added to the CURRENT PLAN, a CPLREC12 POTENTIAL PREDECESSOR record is created, for that application.
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The CPLREC12 lists all the applications in the AD DATABASE that have DEFINED PREDECESSORS in the APPLICATION whose name appears in the CPLAPRE12 field.
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When any occurrence is added to the plan, The CPLREC12 records of all the existing occurrences are searched as part of the DEPENDENCY RESOLUTION processing.
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CPLREC12 logic is entirely within the CURRENT PLAN, and relates to work DYNAMICALLY ADDED to the CP via dialog, PIF, or ETT. It has nothing what so ever to do with CP or LTP batch processing other than that the CPLREC12 record is CREATED as part of CP EXTEND/REPLAN. The record is USED only by MCP (Modify Current Plan) logic.
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So to summarize, the POTENTIAL PREDECESSOR RECORD (CPLREC12) lists those applications in the AD DATABASE which may POTENTIALLY BE SUCCESSORS of the application "owning" that record. Since the CPLREC12 record is architecturally limited to 1000 "nodes", no occurrence DYNAMICALLY added to the CP can ever have PREDECESSORS in more than 1000 DIFFERENT APPLICATIONS.
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On the other hand,
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The ABSOLUTE TOTAL NUMBER OF EXTERNAL DEPENDENCIES, both PREDECESSORS and SUCCESSORS, that can be created when an application occurrence is added to the CP via DAILY PLANNING is listed in message EQQ0522I in the EQQMLOG of the LTP EXTEND and LTP MODIFY ALL batch planning jobs.
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All EXTERNAL DEPENDENCIES for occurrences added to the CP via CP EXTEND are brought forward from the LTP, and the number of external successors and predecessors an application may have in the LTP (as listed in message EQQ0522I) is limited by the MAXRECL of the EQQLTDS, EQQLDDS, and
and EQQLTBKP data clusters.
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So message EQQ0370W indicates that the specified application is pointed to as an external predecessor in the AD database by more than 1000 different applications, and thus that MCP (MODIFY CURRENT PLAN) processing will not be able to resolve all of those defined dependencies should that application be dynamically added to the CP. Message EQQ0370W is issued by CP BATCH planning because that is when the CPLREC12 records are created and that is the only time the databases are cross-checked. It indicates a POTENTIAL FUTURE PROBLEM that the user needs to be aware of.
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Message EQQ0522I indicates the absolute maximum number of external PREDECESSORS *AND* SUCCESSORS that can be created for a given application occurrence by the BATCH PLANNING PROCESS. It is issued by LTP batch processing because it is based on the MAXRECL of the TWSz LTP datasets.
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