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Article ID: 131923


Updated On:


Database Analyzer (IMS Tools) Mainframe Configuration Manager for IMS for z/OS IMS TOOLS - MISC Compress Data Compression (IMS Tools) Database Analyzer for IMS for z/OS Database Copier for IMS for z/OS Database Organizer for IMS for z/OS Mainframe Extended Terminal Manager (IMS Tools) High Performance Recovery for IMS for z/OS Database Organizer (IMS Tools) Mainframe Program Restart Manager for IMS for z/OS Secondary Index Builder for IMS for z/OS Secondary Index for IMS for z/OS JARS JARS Resource Accounting JARS SMF Director JMR MIM Resource Sharing (MIM) MIM Data Sharing (MII) MIM Tape Sharing (MIA) MIM Message Sharing (MIC) Nastel AutoPilot for WebSphere MQ Panvalet QuickFetch Raps VSE Scheduler VSE SMR SOLVE:Operations Automation SOLVE:Access Session Management SOLVE:FTS SYSVIEW Performance Management NXBRIDGE - SYSVIEW/ENDEVOR SOLVE


When does this message get issued?

A "caijtrk"-report actually shows

so nearly the whole CAIJTRK should be free.


Component: SCHDMS


The NJOBS parameter can influence the wrap around situation because when used on the FORMAT command it indicates how big the data area of the tracking file should be. The bigger the data area the less frequently the wrap around message will occur. 

Initially, records are added sequentially to the tracking file. A check is made to see if the record about to be added goes beyond the highest RBA in the data area. If so, the wrap around message is issued and Scheduler then needs to start at the beginning of the data area to find free space large enough to hold the record about to be added.

Going forward this adds a little bit of overhead since a search for free space needs to be done as opposed to just writing the record on the next available RBA. 
Performing a REORG of CAIJTRK will reformat the tracking file placing any records that need to be restored sequentially from the start of the data area. This will allow schedule going forward to process adding the records sequentially until the end of the data area is reached. i.e. wrap around message issued. 

By finding the right mix of how often the REORG job is run and how big the tracking file both in size and NJOBs specification should be, the wrap around message can be avoided.