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Is raw disk access on Mainframe possible?

 
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lucky

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Joined: 01 Jun 2005
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Location: Croatia

PostPosted: Sat Jun 04, 2005 7:16 pm    Post subject: Is raw disk access on Mainframe possible?
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Hello all!

Is raw disk access on MF possible, and if it is, how can I do it?

TIA
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mmwife

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Joined: 30 May 2003
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PostPosted: Sun Jun 05, 2005 12:07 am    Post subject:
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What do you mean by "raw" disk access?
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lucky

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PostPosted: Mon Jun 06, 2005 11:53 am    Post subject:
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mmwife wrote:
What do you mean by "raw" disk access?


A raw disk is a disk, or part of it, that is not formatted by the OS, but can be used by an application to set it's own file system on it. It's a method very popular in DBMSs, like Oracle, Informix...

It is used to store large chunks of data in a format that is more suitable for the application, and in that way gain additional performance.
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grepusr3

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Joined: 10 May 2005
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PostPosted: Tue Jun 07, 2005 1:19 pm    Post subject: Re: Raw disk access
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lucky,

Yes, if you have appropriate (security) authority - Raw disk access is possible on the MF - it is best left for low level assembly - storage developers. You may want to follow up under topic "channel programming". Generally ALL I/O is handled by OS Storage Supervisor (via SVC calls). Most DBMS's uses direct SVC calls for performance reasons (and bypass DFP). Please do not attempt this kind programming at your site, unless you are a DASD Storage developer. The consequencs are unpredictible.

Hope this helps!

-Pelad
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lucky

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PostPosted: Tue Jun 07, 2005 5:32 pm    Post subject: Re: Raw disk access
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grepusr3 wrote:

Yes, if you have appropriate (security) authority ......


Thanks, I'll look it up

grepusr3 wrote:

Please do not attempt this kind programming at your site, unless you are a DASD Storage developer. The consequencs are unpredictible.


Thank God for Hercules! Play with the system, f... it up, and recover it from the beginning icon_smile.gif
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mmwife

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PostPosted: Mon Jun 20, 2005 8:47 am    Post subject:
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I'm sure you can do whatever you like provided you have the execution/access authority and remain faithful to the device architecture and the dictates of the operating system controlling the environment.

If you're thinking of the MF as a chunk of iron and plan on providing your own operating environment, then your choices are bound only by the functioning of the hdware and your ability to provide appropriate pgming support, including microcode.
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