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meenakshi_forum Warnings : 1 Active User
Joined: 27 May 2008 Posts: 121 Location: India
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I would like to know the difference in both Tape and Disk;
advantages of one over another and when each is suggested;
how they work
Thanks. |
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expat
Global Moderator
Joined: 14 Mar 2007 Posts: 8796 Location: Welsh Wales
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So here we go down the old 'site specific' route again.
Performance wise, the answer depends on
a) What specific hardware you have installed
b) How much cache your site has purchased for each individual subsystem.
c) How each subsystem has been configured, with taking (b) into account.
Generally speaking, DASD for availability, tape for volume and/or portability.
But then again having work at a few sites with DASD farms of 300+ Tb, DASD was never an issue for virtually any sized file. |
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gcicchet
Senior Member
Joined: 28 Jul 2006 Posts: 1702 Location: Australia
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Also data on tape cannot be shared, if you have multiple jobs trying to read the data it will be a no goer.
Gerry |
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dbzTHEdinosauer
Global Moderator
Joined: 20 Oct 2006 Posts: 6966 Location: porcelain throne
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tape is more flexible than disk.
fixed disc is the most inflexible.
tape can be repaired, not so easy with a disc.
if you wish to harrass the operations staff, request tapes that don't exist, use multi-reel requests on your jobs to tie up more than one tape drive, request unnecessary (or out of order) tape mounts - that always brings a laugh from the ops-staff. another laugh generator is not specifiying rewind.
As gcicchet said, you can not reserve a disc for only your use, but you can really tie things up with tapes. |
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gcicchet
Senior Member
Joined: 28 Jul 2006 Posts: 1702 Location: Australia
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Concatenating tape datasets can also be fun, the non use of UNIT=AFF can tie up many tape drives unnecessarily.
Incorrect retention period or expiry dates can exhaust the scratch pool.
Gerry |
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expat
Global Moderator
Joined: 14 Mar 2007 Posts: 8796 Location: Welsh Wales
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gcicchet wrote: |
Concatenating tape datasets can also be fun, the non use of UNIT=AFF can tie up many tape drives unnecessarily.
Incorrect retention period or expiry dates can exhaust the scratch pool.
Gerry |
Hey guys, you forgot about writing them too
// UNIT=(TAPE,12)
usually gets the operators on the phone in seconds |
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gcicchet
Senior Member
Joined: 28 Jul 2006 Posts: 1702 Location: Australia
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Writing one 80 byte record to tape is also very popular.
especially if stacking is not available.
Gerry |
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agkshirsagar
Active Member
Joined: 27 Feb 2007 Posts: 691 Location: Earth
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Last few posts should have come with -
CAUTION: DO NOT TRY THIS AT HOME |
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expat
Global Moderator
Joined: 14 Mar 2007 Posts: 8796 Location: Welsh Wales
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agkshirsagar wrote: |
Last few posts should have come with -
CAUTION: DO NOT TRY THIS AT HOME |
That is why we try them at work |
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Garry Carroll
Senior Member
Joined: 08 May 2006 Posts: 1205 Location: Dublin, Ireland
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Quote: |
agkshirsagar wrote:
Last few posts should have come with -
CAUTION: DO NOT TRY THIS AT HOME icon_lol.gif
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... or possibly more to the point....
CAUTION: DO NOT TRY THIS UNLESS YOU WANT TO BE AT HOME - PERMANENTLY !!
Garry |
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006 Posts: 6248 Location: Mumbai, India
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Hi,
Further,
- DASD is only type of media on which VSAM file can resides
- TAPE file can be accessed in a linear way only
- TAPE drives are not "always in service" of your system, they need to be mounted first
- Usually there is a site-specific limit for the use of max. TAPE-drives in a single JOB, however, it's site specific. At my shop it's 12.
- TAPE drives ar usually used for back-ups
- One can't just browse a TAPE drive, one needs to get file on DASD in order to see the contents of the TAPE file.
- When copying data from TAPE to DASD or vice-versa you might waste a lot of sapce due to the DCB information used; what can happen, to understand this, you can check this link - www.ibmmainframes.com/viewtopic.php?t=23225&highlight=sysut1
Here is a link which tells about different type of TAPE-drives - www-03.ibm.com/systems/storage/tape/drives/index.html
And here is a link for DASDs or Disk drives - www-03.ibm.com/systems/storage/disk/index.html |
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006 Posts: 6248 Location: Mumbai, India
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Quote: |
CAUTION: DO NOT TRY THIS UNLESS YOU WANT TO BE AT HOME - PERMANENTLY !! |
Heh heh..giggling...heh heh.. |
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