  Seeking Better I/O Performance? 
 The Question is:
 
What on a VAX system should be modified to increase the speed of truncation of
data files that are created with large allocated size at process start? Is
this a disk MOUNT, set file cache size problem? or an ACP_&lt;cache&gt; issue? or both?
Thank you for your help!
 
 The Answer is:
 
  Most obviously, the speed of the VAX processor and the performance of
  and the typical load on the I/O subsystem would all be of interest
  when seeking to improve I/O performance.  (OpenVMS Alpha systems have
  far faster processors and far faster I/O subsystems.)  Process quotas
  can also enter into the discussion, particularly if overly constrained.
  Depending on the access pattern, storage attributes such as highwater
  marking or erase-on-delete can also have an effect on performance.
 
  The default file extent size value can be set on a system-wide, process,
  volume, or application basis.  Via SYSGEN SHOW/RMS, via SET/SHOW RMS,
  via SET/SHOW DEVICE, or via RMS or XQP service APIs, respectively.
 
  The OpenVMS Performance Management Manual will be of interest, as a
  start.
 
