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Vsam space allocated and usage percent

 
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quanzhong

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Joined: 12 Aug 2008
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Location: china

PostPosted: Tue Sep 23, 2008 8:20 am    Post subject: Vsam space allocated and usage percent
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Hi,
now i met a problem on PRD enviroment on VSAM.
Code:
 
                       Tracks %Used XT  Devi
 AAAA.S1.KE           78000    ?  67  3390
 AAAA.S1.KE.D           202    ?  55  3390
 AAAA.S1.KE.I         20190   99  21  3390


space parameter is
Code:

cyl(50   50)

as its allocated space is close 90K Tracks(because its managed by DATACLASS(VSSML),which limits file size not over 90K tracks), so we suggest to change its DATACLASS, but client said that file only used 35% allocated space.

so my doubt is, how to get the usage percentage? if what he said is true, how to release the allocated but unused space.. thanks.

Ps. we have file-aid tool in our shop.
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quanzhong

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PostPosted: Tue Sep 23, 2008 8:29 am    Post subject:
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sorry,
Quote:


Tracks %Used XT Devi
AAAA.S1.KE 78000 ? 67 3390
AAAA.S1.KE.D 202 ? 55 3390
AAAA.S1.KE.I 20190 99 21 3390

should be changed to
Code:

                                     Tracks %Used XT  Devi
AAAA.S1.KE                                       
AAAA.S1.KE.D                  78000    ?  67  3390
AAAA.S1.KE.I                    202    ?  55  3390

so another question is, when ignore index space parameter, and use jclcheck to check the synax, i will get warning message, and say that lastcc is 12. but in fact, we seldom assign space parameter for index, so how system do that ? thanks..
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expat

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PostPosted: Tue Sep 23, 2008 11:28 am    Post subject:
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IDCAMS LISTCAT ALL will show you the high allocated and high used RBA

(Hi used / Hi alloc) * 100 = % used.
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quanzhong

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PostPosted: Tue Sep 23, 2008 12:59 pm    Post subject:
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Hi, expat
the listcat result
Code:

ALLOCATION                                             
  SPACE-TYPE------CYLINDER     HI-A-RBA------3833856000
  SPACE-PRI-------------50     HI-U-RBA------3813212160
  SPACE-SEC-------------50                             

so used is more than 99%

then i reproed this file to another file, and listcat the new file, and found that space allocated is 35% of the origina file..

more listcat result for the original file
Code:

ATTRIBUTES                                                                 
  KEYLEN----------------22     AVGLRECL------------6549     BUFSPACE-------
  RKP--------------------0     MAXLRECL------------6549     EXCPEXIT-------
  SHROPTNS(2,3)      SPEED     UNIQUE           NOERASE     INDEXED       N
  UNORDERED          REUSE     NONSPANNED                                 
STATISTICS                                                                 
  REC-TOTAL---------161487     SPLITS-CI--------------0     EXCPS----------
  REC-DELETED-------107128     SPLITS-CA-----------4786     EXTENTS--------
  REC-INSERTED------233928     FREESPACE-%CI----------0     SYSTEM-TIMESTAM
  REC-UPDATED----------233     FREESPACE-%CA----------0          X'C308FE7F
  REC-RETRIEVED---51091680     FREESPC-------2497085440                   

this file is KSDS, and as you can see, there are frequently deletes and inserts every day, is there any way to release the unused space fragment, split, except delete, re-define, then repro?
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expat

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PostPosted: Tue Sep 23, 2008 1:22 pm    Post subject:
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How many extents has it extended to at the moment ?
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quanzhong

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PostPosted: Tue Sep 23, 2008 1:37 pm    Post subject:
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Hi
Code:

EXCPS------------8534497
EXTENTS---------------67
SYSTEM-TIMESTAMP:       
     X'C308FE7F1D2F52C4'

now already 67 extends
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expat

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PostPosted: Tue Sep 23, 2008 1:42 pm    Post subject:
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I would consider performing a periodic reorg of the file

Use either EXPORT & IMPORT

or REPRO to flat file, delete / define the cluster, and the REPRO from the flat file back to the cluster.
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quanzhong

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PostPosted: Tue Sep 23, 2008 1:47 pm    Post subject:
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Hi, expat.

Ok, i will try to persude the client. thanks.
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expat

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PostPosted: Tue Sep 23, 2008 1:53 pm    Post subject:
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Your cluster has 65% free space in it, but because of the CA splits the free space is spread aound and may become unusuable depending on the position within the file that inserts / deletes occur.

A periodic reorg will recoup the free space and ensure that it is totally usable again until the same situation arises once more.
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Robert Sample

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PostPosted: Tue Sep 23, 2008 4:59 pm    Post subject:
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What's the data CISIZE and the index CISIZE? It's unusual to have so many CA splits without CI splits.
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quanzhong

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PostPosted: Tue Sep 23, 2008 7:56 pm    Post subject:
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Hi, Robert
Quote:

What's the data CISIZE and the index CISIZE? It's unusual to have so many CA splits without CI splits.

it also confused me. we didn't assign CASIZE and CISIZE, it muse be use the default value, bue how can i find out that?
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Robert Sample

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PostPosted: Tue Sep 23, 2008 8:00 pm    Post subject:
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LISTCAT will contain the CISIZEs. Default values are likely to be quite bad for this file.
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quanzhong

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PostPosted: Wed Sep 24, 2008 7:16 am    Post subject:
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Hi, Robert
I got the LISTCAT info about CISIZE and CI/CA.
Code:

ATTRIBUTES                                                 
  KEYLEN----------------22     AVGLRECL------------6549     BUFSPACE-----------17920     CISIZE--------------8192
  RKP--------------------0     MAXLRECL------------6549     EXCPEXIT----------(NULL)     CI/CA-----------------90
  SHROPTNS(2,3)      SPEED     UNIQUE           NOERASE     INDEXED       NOWRITECHK     NOIMBED       NOREPLICAT
  UNORDERED          REUSE     NONSPANNED   
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Robert Sample

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PostPosted: Wed Sep 24, 2008 5:41 pm    Post subject:
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With CISIZE of 8192, you're wasting 1643 bytes per CI or 20% (ignoring overhead bytes). Setting CISIZE to 26624 would allow half track blocking and reduce the wasted bytes per CI to about 1%. You probably should assign CA freespace to allow for the record inserts, maybe FRSP(0 10)?

78,000 tracks represents 468,000 control intervals which are holding 161,487 records at one per CI. It sounds like a good bit of the free space is in the CA splits, so a frequent unload / delete / define / reload to get rid of the CA splits would also keep the free space at a minimum.
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