Queue server automatic ALTER processing

The queue server monitors the total number of elements and entries in use in the structure, using information returned by the coupling facility on every request.

When the numbers in use exceed the specified thresholds, a warning message, DFHXQ0411 or DFHXQ0412, is issued, and is repeated each time the number in use increases beyond further thresholds.

Each time the warning is issued, the server tests whether an automatic ALTER for the entry to element ratio should be performed. The test is done by calculating how many excess elements or entries will be left when the other runs out completely. This is based on the ratio between the current numbers of elements and entries in use.

An IXLALTER request is issued to alter the entry to element ratio to the actual current ratio between the number of entries and elements in use if:
  • The number of excess elements or entries exceeds the number specified in the ALTERELEMMIN or ALTERENTRYMIN parameter, and
  • The same number expressed as a percentage of the total exceeds the value specified in the ALTERELEMPC or ALTERENTRYPC parameter

Only one ALTER request may be active at a time for a given structure. If the ALTER process is started by one server, the ALTER of another server will be rejected. However, the system automatically notifies all servers when the ALTER completes, giving the new numbers of elements and entries so that each server can update its own status information.

A further ALTER attempt is suppressed until at least the minimum ALTER interval (specified by the ALTERMININTERVAL parameter) has elapsed, if:
  • Any form of ALTER has already been used recently (by any server or by an operator SETXCF ALTER command), and
  • The structure space usage has remained above warning levels since the previous attempt.
Parent topic: Setting up and running a temporary storage server

dfha2_queueserver_auto_alter_processing.html | Timestamp icon Last updated: Thursday, 27 June 2019