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XQP performance and directory cache size?

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The Question is:

Dear wizard,
I have some questions about:
==>>> directory cache limits
Originally OpenVMS/RMS wouldn't cache directories larger than 128 blocks.
 OpenVMS/VAX (mind: VAX, not AXP) V7.2 release notes state:
...Beginning with Version 7.2, RMS attempts to cache directories of any size.
 If memory or other resources are not available to cache the file, wildcard
 lookups are then directed to the file system.
Is/was there such a limit in OpenVMS/Alpha? If the limit still exists, what is
 the actual size for VMS V7.2-1?
Thanks, Ton.

The Answer is :

  Both OpenVMS VAX and OpenVMS Alpha behave similarly in this area.
  While the OpenVMS Wizard would still not encourage storing huge numbers
  of files in a single (very large) directory, the directory caching limits
  have been greatly increased on OpenVMS VAX and OpenVMS Alpha, starting
  with OpenVMS V7.2.  As part of work on improving overall directory and
  file system performance, it was found that a significantly larger benefit
  was derived from various improved directory I/O operations than was
  found through the increase to the size of the directory cache.
  As should be obvious, the improved directory I/O performance will benefit
  all OpenVMS applications -- including those with large directory files and
  those with rather more typical directory sizes, regardless of the caching
  of individual directories.
  Work expected in V7.3 on file system caching should provide additional
  improvements for read-ahead and related file caching, with the addition
  of support for write-behind caching expected in a subsequent release.
  And yes, the OpenVMS Wizard is quite deliberately being obscure about the
  new directory cache sizing.  As stated earlier, the OpenVMS Wizard cannot
  and does not recommend storing large numbers of files in a single (very
  large) directory.

answer written or last revised on ( 18-OCT-2000 )

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