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ENQ option in PL/I

 
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Bharath Nadipally

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Joined: 24 Jun 2008
Posts: 22
Location: Hyderabad

PostPosted: Thu Mar 12, 2009 1:31 pm    Post subject: ENQ option in PL/I
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Hi,

I have read somewhere that ENQ option can be used for PL/I program. Can someone tell me what is it about?


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Bharath
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Bill O'Boyle

CICS Moderator


Joined: 14 Jan 2008
Posts: 2504
Location: Atlanta, Georgia, USA

PostPosted: Thu Mar 12, 2009 6:49 pm    Post subject: Reply to: ENQ option in PL/I
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ENQ, along with its counterpart, DEQ, are not part of the PL/I Language base.

Assuming this is PL/I Batch, ENQ/DEQ are available as Assembler Language Macros, which are coded in Assembler sub-program's and Called from a given language, such as PL/I.

If this is CICS (regardless of the language), there are ENQ/DEQ commands (API's), which are part of CICS itself.

When you issue an ENQ, you're attempting to gain exclusive control over a known target RESOURCE, which can be a FILE, a FIELD, a TABLE, etc. If the RESOURCE is already ENQ'd then the program could either WAIT for the RESOURCE to free or inform the Caller or Program that the RESOURCE is currently unavailable.

What is the purpose for using an ENQ? Normally, it's very selective and specialized and the large majority of Application programs don't ever use ENQ nor DEQ, unless the reasons are compelling.

On the flip-side, when you're done with the ENQ of the target RESOURCE, a DEQ must be issued, removing exclusivity.

Regards,
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