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What is the significance of ALIAS?

 
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Mariraj

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Joined: 09 Jul 2007
Posts: 59
Location: Chennai

PostPosted: Thu Sep 04, 2008 3:01 pm    Post subject: What is the significance of ALIAS?
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Hi,

I executed the following piece of code.

Code:
     GENERATE  MAXNAME=3,MAXGPS=1   
       MEMBER  NAME=(MEMBER4,FOURTH)
GROUP1 RECORD  IDENT=(1,'1',1)     
       MEMBER  NAME=MEMBER5         


This code is to create 2 members from the input seq. file and add it to the existing output PDS.

The second line in the above code creates an alias(FOURTH) to the member MEMBER4. What is the significance of this alias?. As I looked into the PDS, I could see that it is just a copy of MEMBER4.

I just coded this because I saw a similar example in the IBM reference material.

All I want to know is, what is the significance of creating this alias?
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expat

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Joined: 14 Mar 2007
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Location: Back in jolly old England

PostPosted: Thu Sep 04, 2008 3:09 pm    Post subject:
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An alias allows you to access a dataset or member from the alias name as well as the base name.
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Mariraj

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PostPosted: Thu Sep 04, 2008 3:30 pm    Post subject:
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Thanks for the reply Expat.

I agree with what you said. I have seen alias for the entire PDS.

XXXX.C8757.LOAD -> Instead of typing this, we can type XXXX.CURRENT.LOAD. Here current refers to the current cycle(C8757) and XXXX.C8757.LOAD will be opened.

This will be helpful since one need not know the current cycle or date. This is just an example I am quoting.

I think here it holds some purpose.

But will alias be so useful for members too?.
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Bill Dennis

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Joined: 17 Aug 2007
Posts: 562
Location: Iowa, USA

PostPosted: Thu Sep 04, 2008 6:51 pm    Post subject:
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It is more common for load libraries. For example, member names SORT and ICEMAN are alias names for member IERRCO00.
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Anuj Dhawan

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Joined: 22 Apr 2006
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Location: Mumbai, India

PostPosted: Thu Sep 04, 2008 9:23 pm    Post subject:
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Hi,

Just to add my bit, as they say for my $ 0.2..

ALIASes, to keep it simple, are just pointers, between catalogs. Leave the multilevel aliasing for now. Search for a dataset is structured on a tree starting from the "master-catalog", the search follows two different paths -

1. a search on the full dataset name- if found good.. STOP the search.

2. a search on the ALIAS ( nothing but the high level qualifier), if found the the ALIAS will point to another catalog where a search will be performed on the full dataset name


There are two main reason to use aliases:

- performance reasons not to have too many read write requests against a single catalog ( if everything was cataloged in the master-catalog the system might pretty soon become unusable.

- security to allow access to the catalogs based on the need to use.
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Bill Dennis

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PostPosted: Fri Sep 05, 2008 2:53 am    Post subject:
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Good explanation of dataset alias names, Anuj, but Mariraj is now concerned with member name aliases within a PDS directory.

Multiple names can refer to the same module for convenience.

The alias name might even have a different entry point into the load module code. Two different execution starting points for different uses.
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