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why JCL has //


IBM Mainframe Forums -> JCL & VSAM
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vidhyanarayanan

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Joined: 23 Dec 2005
Posts: 52

PostPosted: Wed Apr 19, 2006 3:21 pm
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Hi all,

why JCL has slashes // in col1 and col2 of each STATEMENT?
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dneufarth

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Joined: 27 Apr 2005
Posts: 419
Location: Inside the SPEW (Southwest Ohio, USA)

PostPosted: Wed Apr 19, 2006 7:22 pm
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identifies it as JCL as opposed to inline data or JES control statements
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pspreddy

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Joined: 14 Mar 2006
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Location: Chicago

PostPosted: Thu Apr 20, 2006 1:22 am
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The identifier field is the first field in a JCL statement.

Two slashes, //, in positions 1 and 2 instruct the computer to expect a JCL statement.

A slash and an asterisk (/*) in positions 1 and 2 identify a JES2 statement.

If you are entering data, omit the identifier.

Thanks
Shiva
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Bharanidharan

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Joined: 20 Jun 2005
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Location: Chennai, India

PostPosted: Thu Apr 20, 2006 3:43 pm
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The root goes far back in time!
The pioneers, when designing a language for MVS to interpret which they knew would be used forever, arrived at a consensus that all JCL commands/statements to be appended with // in the punched cards such that card reader would know that the cards necessarilly contain commands to get the job done in mainframe.
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superk

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Joined: 26 Apr 2004
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Location: Raleigh, NC, USA

PostPosted: Fri Apr 21, 2006 9:09 pm
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Back when punched cards were used to submit JCL, if the cards were mistakenly loaded into the reader incorrectly, the slashes wouldn't be read first and the card deck would be rejected.
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