On Fri, 25 May 2007 14:14:44 -0400, Bruce Black wrote:
>
>As far as a EXC-SHR function, this also seems obvious to me. The
>initiator ENQs the dataset, and then releases the dataset at the end ofVVe
>the last step that uses it. If you issue a EXC-SHR request, a fullowing
>step may need the dataset exclusive and you have now compromised the
>dataset. There is no easy way that I know to determine if the current
>step is the last step that uses the dataset.
>
Apparently the initiator is up to the task, easy or difficult.
The JCL fragment:
//*
//STEP1 EXEC PGM=IKJEFT01
//SYSUT1 DD DISP=OLD,DSN=FOO.BAR,
// UNIT=SYSALLDA,VOL=SER=TSO001
//SYSTSPRT DD SYSOUT=(,)
//SYSTSIN DD *
free dd(sysut1)
free dd(sysut1)
//*
//STEP2 EXEC PGM=IKJEFT01
//SYSUT1 DD DISP=OLD,DSN=FOO.BAR,
// UNIT=SYSALLDA,VOL=SER=TSO001
//SYSTSPRT DD SYSOUT=(,)
//SYSTSIN DD *
free dd(sysut1)
free dd(sysut1)
//*
produces SYSTSPRT from STEP1
READY
free dd(sysut1)
READY
free dd(sysut1)
IKJ56247I FILE SYSUT1 NOT FREED, IS NOT ALLOCATED
READY
END
... and SYSTSPRT from STEP2
READY
free dd(sysut1)
READY
free dd(sysut1)
IKJ56247I FILE SYSUT1 NOT FREED, IS NOT ALLOCATED
READY
END
... so even though FOO.BAR was FREEd in STEP1, the initiator
was able to allocate it again in STEP2. I hope this was
not done without an ENQ. Whatever technique the initiator
used here, it could use the same technique to differentiate
an EXC from A SHR ENQ.
-- gil
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