IBM Mainframe Forum

Hello,

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



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 :



th dataset took 5 volume only instead of 59...

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.

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.



when it works, i have that :

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.

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



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

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.

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.

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