Fast volume



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Fast volume

Postby samb01 » Mon Jun 11, 2018 5:41 pm

Hello,

i the sysout of a job; i got this message :


IGD17294I FAST VOLUME SELECTION IS USED TO ALLOCATE DATA SET
 


I found the page ibm : https://www.ibm.com/support/knowledgece ... g87507.htm

but i'm sorry it's difficult to anderstand because of my english...

I could tell you what i anderstood :
The dataset didn't find enought space so SMS actived the Fast Volume, but i can't anderstand what SMS do when the Fast volume is actived.

In fac, my dataset was succesfully allocated (without error) but the dataset was not good because when a job try to read this dataset, we have the mesdssage :


IEC020I 001-3,HCVGFSQDT,BN1,SYSUT1-0021,522A,GVHU77,MY.DATASET        
IEC020I NON-ACCEPTABLE ERROR          

 


th dataset took 5 volume only instead of 59...
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Re: Fast volume

 

Re: Fast volume

Postby Robert Sample » Mon Jun 11, 2018 5:51 pm

The manual message makes it clear:
When fast volume selection is used, SMS will first select volumes normally until 100 volumes have been rejected for insufficient free space. At this time, SMS issues this message and excludes volumes that do not have sufficient free space in SMS volume statistics from further selection.
So SMS attempted to allocate your data set on 100 different volumes, all of which were rejected because they did not have enough free space for your allocation. After the 100 volumes have been attempted, SMS rejects all volumes without sufficient free space without attempting to allocate on them.

If you had problems with the data set, you REALLY need to talk to your site support group's storage management team for help. Nobody on this forum works at your site and the issue you experienced is specific to your site.
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Re: Fast volume

Postby samb01 » Mon Jun 11, 2018 8:21 pm

I just can't anderstand why the dataset slect only 5 volumes instaed of 59 because, in the JCL there are : VOL=(,,,59)

and it is guaranteee space.


IGD17294I FAST VOLUME SELECTION IS USED TO ALLOCATE DATA SET W.SAVEP.G0012V00
IGD17070I DATA SET X.SDVE.RDFR                            
ALLOCATED SUCCESSFULLY WITH 5 STRIPE(S).                                    
IGD17160I DATA SET X.SDVE.RDFR                                     

 


when it works, i have that :


IEF237I DMY  ALLOCATED TO CHKPT                
IGD17070I DATA SET W.SAVEP.G0016V00            
ALLOCATED SUCCESSFULLY WITH 59 STRIPE(S).      
IGD17160I DATA SET X.SDVE.RDFR          
IS ELIGIBLE FOR COMPRESSION                    
IGD101I SMS ALLOCATED TO DDNAME (SAVEP   )    
        DSN (X.SDVE.RDFR            

 
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Re: Fast volume

Postby Robert Sample » Mon Jun 11, 2018 9:07 pm

The VOL parameter tells the system the MAXIMUM number of volumes your data set may use. If it does not require that many, it will not use that many. I think you misunderstand how guaranteed space works. From the Storage Administration manual (emphasis added by me):
For a multivolume system-managed data set, the system preallocates primary space on all the volumes. The first volume becomes the primary volume. The remaining volumes become candidate volumes with preallocated space. The system operates differently depending on what the user codes for DISP.

When the existing allocated space on the current volume becomes full with DISP=NEW or MOD, the system attempts to create secondary extents on the current volume. If not enough space is left on the current volume, the system uses the preallocated primary extent on the next volume. The system converts this next volume from a candidate volume to a primary volume.
In other words, you most likely have 54 preallocated primary extents for this data set, but they are still just candidate volumes until the space is required.
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Re: Fast volume

Postby samb01 » Tue Jun 12, 2018 12:29 pm

Hello,
may be the problem is the allocation of the secondary extent.

At the beginning, the allocation was :

SPACE=(CYL,(1000,400),


If the system does not found 1000 cyl in 59 volumes. It abends before starting. So i think the problem is in the secndaty allocation.

May the solution is to use 50 cylinders instead of 400 cylinders in the secondary allocation to make sure SMS will found the secondary sopace and prevent it to use FAST VOLUME SELECTION


SPACE=(CYL,(1000,100),
 


Just fo r information, when it abends, the message is :


IGD17272I VOLUME SELECTION HAS FAILED FOR INSUFFICIENT SPACE FOR  163
DATA SET MY.DATASET
REQUESTED SPACE QUANTITY = 830039 KB
STORCLAS (SC1) MGMTCLAS (MC1) DATACLAS (DC1)
STORGRPS (SG1  )                                    
IGD17292I DATA SET MY.DATASET IS NOT  164          
ELIGIBLE FOR SPACE CONSTRAINT RELIEF BECAUSE IT IS A    
MULTI-STRIPE DATA SET

-JOBNAME  STEPNAME PROCSTEP    RC   EXCP    CPU    SRB  CLOCK   SERV
-IEFACTRT A        TXX      FLUSH      0    .00    .00   2.34      0

IEF453I JOB1 - JOB FAILED - JCL ERROR - TIME=12.23.30  

                                   
                                       

 
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Re: Fast volume

Postby expat » Wed Jun 13, 2018 11:16 am

If you know the RECFM, LRECL and an estimate of the number of records you could actually calculate the space requirement and then divide that over say 30 volumes with secondary extents kept to around 10% of the primary. That always worked for me in the past.
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Re: Fast volume

Postby Robert Sample » Wed Jun 13, 2018 4:52 pm

You REALLY need to learn how to believe what the computer tells you -- it does not lie to you. Secondary space allocation has NOTHING to do with your problem. You posted
IGD17272I VOLUME SELECTION HAS FAILED FOR INSUFFICIENT SPACE FOR 163
DATA SET MY.DATASET
REQUESTED SPACE QUANTITY = 830039 KB
Note that 830039 KB is 1000 cylinders -- so the problem you are having is finding a single volume with 1000 cylinders available; the system is telling you that no single volume has that amount of free space on it (the system may use up to 5 extents for the primary space allocation, so none of your volumes have 1000 cylinders available in at most 5 extents).
may be the problem is the allocation of the secondary extent.
No, because secondary extents are not allocated until the primary has been allocated, and the data set needs additional space -- only then will secondary space be looked at. As long as you are looking at the secondary space allocation, you will never be able to resolve your problem. Now, if you had changed your space to (CYL,(500,500)) or (CYL,(500,1000)) even -- that might have allowed the data set to allocate (depending upon the volumes).

Have you asked your site support group, and specifically the storage management group, for assistance? If not, why not -- they should be your FIRST point of contact with this type of issue.
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Re: Fast volume

Postby samb01 » Wed Jun 13, 2018 9:26 pm

Thank you for the explanation. I am juste beginner in storage Management.
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