Disposition SHR - Append or Overwrite

ragin · New User Joined: 20 Feb 2005 Posts: 16

Hello Friends,
1. If i am opening a file in output mode which has disposition as SHR then what will happen if i am writing in to it.

options are

a. it will get append to it.
b.it will get overwrite.

2.If i am opening a file in output mode which has disposition as MOD
then what will happen if i am writing in to it.

options are

a. it will get append to it.
b.it will get overwrite

Please reply to these questions immediately.

vishal_09 · New User Joined: 16 Feb 2005 Posts: 6 Location: hyderabad

hii
if u want to append u must open a file in i-o mode ...............if the file already exist...else u can open in output mode.................

mainframemouli · New User Joined: 01 Mar 2005 Posts: 52 Location: Mysore

Heres the Small answer for your BIg Doubt.

If File Disp filed in JCL for a file is SHR and if u opened the file in output mode then, whatever you write into that file will be overwritten.

if the File Disp field in JCL for a file is MOD and if the file in ouput mode then, whatever you write into the file will be appended.

hope this helps.

mmwife · Super Moderator Joined: 30 May 2003 Posts: 1592

Hi vishal,

You don't have to open a file I/O to append to it. You can do either of the following:

1) Open it output extend
2) Code MOD in the DISP for the file.

P.S. Writing to a file using SHR can be dangerous. This allows simultaneous updates to the file, leaving it open to being "corrupted". I.e. damaged.