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ISMF Difference between volume count and DVC

 
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upendrasri

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Joined: 28 Sep 2017
Posts: 55
Location: India

PostPosted: Tue Dec 05, 2017 12:40 pm    Post subject: ISMF Difference between volume count and DVC
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Hi All,

I would like to understand the deffence between Voume count and Dynamic volume count in ISMF Dataclass?

I have gone through DFSMSdfp Storage Administration mauals.

Volume count is the maximum number of volumes which dataset can expand.

Dyanamic volume count is the maximum number of volumes which can be added dynamically to a dataset.

Both Volume count + Dynamic Voulme count should not cross 59 volumes.

See the below example.

One of my old dataset : TTSS.Z120.TEST --> This is a VSAM Multivolume dataset.

From File Aid(And LISTC also shows same information) using Dataset Utility option we can see the below details.

Code:

DATA COMPONENT: 'TTSS.Z120.TEST.DATA'                   
  Volume Allocations:                                     
   1. A4N138  2. A4N204  3. A4N12A  4. A4N1B6  5. A4N121   
   6. A4N1FE  7. A4N115  8. A4N1CE  9. A4N1G3 10. A4N208   
  11. A4N167 12. *      13. *      14. *      15. *       
  16. *      17. *      18. *      19. *      20. *       
  21. *      22. *      23. *      24. *      25. *       
  26. *      27. *      28. *      29. *      30. *       
  31. *      32. *      33. *      34. *      35. *       
  36. *      37. ______ 38. ______ 39. ______ 40. ______   


Current dataset Used volumes : 11
Total Available volumes for this dataset : 36

From Listc of the above dataset

Code:

CLUSTER ------- TTSS.Z120.TEST                             
     IN-CAT --- USER.TEST.CATALOG                           
     HISTORY                                                   
       DATASET-OWNER-----(NULL)     CREATION--------2017.337   
       RELEASE----------------2     EXPIRATION------0000.000   
     SMSDATA                                                   
       STORAGECLASS ---STANDARD     MANAGEMENTCLASS--PRDINS1   
       DATACLASS ------EXTEND30     LBACKUP ---0000.000.0000   


From ISMF DATACLASSE EXTEND30 we can see the below details.

Code:


TEST1                           DATA CLASS LIST                               
Command ===>                                                  Scroll ===> HALF
                                                      Entries 1-1 of 1         
                                                      Data Columns 12-16 of 52
CDS Name : ACTIVE                                                             
                                                                               
Enter Line Operators below:                                                   
                                                                               
     LINE       DATACLAS SPACE      RETPD OR    VOLUME  ADDITIONAL  DYNVOL     
     OPERATOR   NAME     DIRECTORY  EXPDT       COUNT   VOLUME AMT  COUNT     
    ---(1)----  --(2)--- --(12)---  ---(13)---  -(14)-  ---(15)---  -(16)-     
                EXTEND30    ------  ----------       1  ---------       30     
    ----------  -------- ------  BOTTOM  OF  DATA  ------  --------  ----------



As per ISMF Maximum number of volumes available for this dataset is 1 + 30 ---> 31 ----> correct me if I am wrong?

But currently as per File Aid Maximum available number of volumes for this data set is 36

is it like after reaching Maximum 31 volumes , Manually 5 dynamic volumes added to this data set?
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expat

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Joined: 14 Mar 2007
Posts: 8686
Location: Back in jolly old England

PostPosted: Tue Dec 05, 2017 1:13 pm    Post subject:
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Excuse me, but what the hell has this question have to do with CLIST or REXX ???
Please learn to think about WHERE you post anything before you post it

Because I have to think about where I have to move it to
icon_evil.gif icon_evil.gif icon_evil.gif

How many volumes are defined to the storage group
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upendrasri

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Joined: 28 Sep 2017
Posts: 55
Location: India

PostPosted: Tue Dec 05, 2017 1:22 pm    Post subject:
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Hi Expat,

Sorry, One of my forum is open and I just thought of starting a new topic and posed from there... didn't observe that am in Rexx forum.

There are 110 volumes defined in Storage Group.

If you want am okay to open a new topic outside CLIST or Rexx forum.


Thanks.
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Pete Wilson

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Joined: 31 Dec 2009
Posts: 461
Location: London

PostPosted: Mon Jun 11, 2018 2:47 pm    Post subject:
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Volume Count is the number of volumes the dataset is initially allocated on.

Dynamic Volume Count is invoked if the initial volumes are full and the dataset needs to extend further, at which time the extra 'candidate' volumes (those showing as an asterisk) are added by DVC. The candidate volumes are converted to real volumes as the dataset extends to an extra volume.

DASD datasets cannot have more than 59 volumes as you say. So Volume Count and Dynamic Volume count cannot exceed that, but can be less and that lesser figure becomes the limit.

Also be aware that for every volume whether candidate or real uses about 4k of the TIOT so if you have the numbers too high you can run out of TIOT space which is only 64k, especially if there's a lot of DD's in your job as well. If you have XTIOT enabled it's less of an issue.
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Robert Sample

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Location: Dubuque, Iowa, USA

PostPosted: Mon Jun 11, 2018 6:36 pm    Post subject:
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If you use the online help on the ISMF screen, you will find it explicitly stated that the Data Class DYNVOL COUNT value can be overridden with JCL or other allocation methods, and overrides will not appear in the data column.
Quote:
is it like after reaching Maximum 31 volumes , Manually 5 dynamic volumes added to this data set?
No, the actual behavior will depend upon what your JCL allocates. You can still use up to 59 volumes for a single data set.
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Pete Wilson

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PostPosted: Mon Jun 11, 2018 8:00 pm    Post subject:
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you can also do IDCAMS ALTER dsn ADDVOLUMES(* * *) to add more candidate volumes for existing datasets
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