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* TECH NOTE CD602.T03                                  OCT 1994                 

*                                                                               

* KEYWORDS: AREA LOCK IDMS STARTUP CT406.017                                    

*                                                                               

* DB-90S RELEASE 4.2 TAPES : C60201                                             

*                                                                               

* DB-90s.                                                                       

* When IDMS sets the area locks at startup it will write the                    

* database page with the area lock to disk before updating                      

* the JHDA on the journal file.                                                 

* This means that if IDMS abends in-between writing the database                

* page and the journal records to disk, then warmstart will not                 

* unlock that area and a message DATABASE LOCKED will appear                    

* later in startup.                                                             

*                                                                               

* This is the way IDMS works as it is deemed safer to set the                   

* area lock before updating the JHDA rather than the other way round.           

* In this event there will be one area only locked at startup                   

* and it is quite safe to use IDMSPFIX to unlock the area.                      

*                                                                               

* With DB90s installed, if an IDMS system is very tight on storage              

* below the line then it it possible that an MVS routine might                  

* not be able to allocate a control block and IDMS could abend                  

* while area locks are being set.                                               

*                                                                               

* In principle it is best to maximise the amount of available                   

* storage below the line by setting FREESTG to the highest value                

* possible. See Tech note T9306320 for further details.                         

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