Browse Prior Art Database

Logging Units of Work in a Transaction Processor

IP.com Disclosure Number: IPCOM000116686D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Normington, G: AUTHOR

Abstract

In a transaction processor system such as CICS/ESA it is required to log which Units Of Work (UOW) are present in the system during activity keypointing. The purpose of doing this is to make it possible to deduce, on system restart, how far back the log need be scanned.

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Logging Units of Work in a Transaction Processor

      In a transaction processor system such as CICS/ESA it is
required to log which Units Of Work (UOW) are present in the system
during activity keypointing.  The purpose of doing this is to make it
possible to deduce, on system restart, how far back the log need be
scanned.

      This is typically implemented by scanning the UOW's and logging
each one in turn.  The overhead of this is roughly proportional to
the number of UOWs, and the process can accordingly be inefficient.

      By following steps 1 - 3 below, the efficiency of the logging
process can be considerably improved.
  1.  At the start of the activity keypoint, scan the UOWs and flag
       each one as needing to log during the keypoint.
  2.  When a UOW logs, switch off the flag.
  3.  At the end of the activity keypoint, scan the UOWs again and
log
       each UOW which is flagged.

      The described solution, because it relies upon not logging UOWs
which will log for themselves, substantially reduces the overhead
referred to above.

UOWs fall into the following categories:
  o  UOWs which exist at the start of the keypoint and which
terminate
      without logging before the end of the keypoint.  These need not
      be logged as, in terms of log records, they do not overlap the
      start of the keypoint and therefore do not need to be scanned
on
      a system restart.
  o  UOWs which exist a...