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How to solve tape GDG contention

 
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nemo_budd

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Joined: 30 Mar 2008
Posts: 7
Location: Pune

PostPosted: Fri Nov 06, 2009 8:59 pm    Post subject: How to solve tape GDG contention
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Hi,

we have to execute some of our report jobs on every month starting, once the tape GDG is available. If two jobs are running at same time using the same GDG , then the second job resulting in to contention error. Due to this we have to execute the jobs in sequence and it taking more time to complete all the monthly jobs.

Please suggest me a solution to over come this issue ? How to make the this tape GDG as multi user access, atleast 2 or 3 jobs can access at a time.

Is there any other work around to overcome the contention also welcome.

Thanks,
Kumar
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Robert Sample

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Joined: 06 Jun 2008
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Location: East Dubuque, Illinois, USA

PostPosted: Fri Nov 06, 2009 9:05 pm    Post subject:
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So you're basically asking how to let two jobs read the same tape at the same time? Think about it for a minute -- if job 1 just read block 317 and job 2 wants to read block 1, how is it going to do so?

Tapes are sequential by nature and cannot be shared in the same way data sets on disk can. Disk data sets can have different jobs reading different tracks without an issue, but a tape data set only can be reading at one spot at a time. It does not matter if the data set is a GDG or not, the tape is sequential. You could move the data to disk and allow multiple jobs to use the data set at the same time, but if you cannot move the tape data to disk then you are stuck.
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nemo_budd

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PostPosted: Fri Nov 06, 2009 9:19 pm    Post subject:
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It has arised in my mind :-)

When I am googling i found that some virtual tapes can be accessed by multi user's. So I thought of putting this up here, that am missing any options in the tape storage part. Thanks for your reply, Robert.
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Robert Sample

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PostPosted: Fri Nov 06, 2009 9:21 pm    Post subject:
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From Wikipedia:
Quote:
A virtual tape library (VTL) is a data storage virtualization technology used typically for backup and recovery purposes. A VTL presents a storage component (usually hard disk storage) as tape libraries or tape drives for use with existing backup software.
A virtual tape that is disk-based can be shared, of course -- but if it's a tape drive, it's a tape drive and must be sequentially processed.
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