Getting Space Abends: IEF257I ... SPACE REQUESTED NOT AVAILABLE

Document ID : KB000045533
Last Modified Date : 14/02/2018
Show Technical Document Details

Issue:

There are two situations that can cause space abends with a message like:
 
IEF257I ... SPACE REQUESTED NOT AVAILABLE
 
1. CA Allocate is managing a very large nonSMS DASD pool with very high
utilization.  There are occasional space abends even for just 1 CYL...

2. When several jobs start at the same time, occasionally abends occur...
  
  
Cause:

If you are running your DASD at extremely high utilization, it is very difficult to be
100% effective preventing space abends. There can be just too many allocations
flying about within micro-seconds so that if the needed space is available in one ms,
it can be gone in the next ms before that allocation can be completed.
But, there are some options in CA Allocate that can be turned on to help.
 
 
Resolution:

There were different resolutions for each of the situations noted above.
However, both solutions are very much worth implementing so you cover all the bases.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 
In the VDSTORGP member which defines the nonSMS Storage Groups, values can be
entered in cols 10-11 to indicate the amount of freespace to maintain on the
volumes.  This field defaults to "00" meaning that CA Allocate will not make
any effort to maintain any free space on the volume.
This was the cause of abends for lack of space for even trivial size data sets.
And as importantly, this forces many multi-volume data sets because a data set
already on the volume has no free-space on that volume to take another extent.
So, it is vital that a free space value like "10" or "20" is specified in VDSTORGP
for all the volser entries so that Allocate can maintain some free space for new
allocations and to allow data sets to take extents.
 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
Specify these sysparms in the Vkgparms member that will help the allocation process.
For each of these, the default is 'N', that the feature is inactive.

PLSOPT20 (Y) - Randomize volume selection.

PLSOPT31 (Y) - The ALLOC Environment will re-drive SMS allocation requests for new
non-VSAM data sets when requests fail for sufficient free space. (PLSOPT10 (Y) must also be set.)
 
PLSOPT41 (Y) - Volume selection will be redriven for new nonSMS VSAM in the event
a Space Not Available condition occurs with the chosen volume.
 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   
Additional Information:

If you add those sysparms to your Vkgparms member, then you only need to enter
this command to make them active:  F vam,PARMREF
 
Full description of the VDSTORGP member can be found in the CA Allocate User Guide,
r12.5, Second Edition, Ch 3, Implementation, pg 181, topic: Creating a Storage Group
Definition, aka, Parmlib member VDSTORGP, and specifically pg 183, Free-Space Threshold.

Please see Knowledge Doc TEC565055 which details how the DIF-RTF variables are used.