Expert Advice

NAS_AA_RS_LatencyExceeded  
Situation Description
Suggested Actions
Situation Description

This situation is triggered when the average latency has reached a warning level. Latency can also be defined in a System Automation for z/OS policy and should match the latency that is defined in the situation formula. The average latency is the average elapsed time in milliseconds between the time that transactions were committed to the source table or database and the time that transactions were committed to the target table or database. This average includes only the transactions that were processed during the last polling interval.

When the situation becomes true, NetView message AQN008I is issued as a notification for automation by the Geographically Dispersed Parallel Sysplex® (GDPS®) solution.

When the situation is resolved (becomes false), NetView message AQN008I is issued again as a notification for automation by the GDPS® solution.

 

Suggested Actions

DB2 Replication: The average latency as reported by DB2 Replication can be monitored by the IBM InfoSphere Replication Server Q Replication Dashboard. Moving graphs in the dashboard track real-time replication throughput, latency, and the fullness of message queues (queue depth). You can view live graphs that display Q Capture and Q Apply throughput, log latency, and end-to-end latency. The dashboard summary helps you quickly identify and troubleshoot problems, and shows at-a-glance status information on programs, queues, Q subscriptions, and other objects.

See the Q replication tuning section in the IBM Information Management Software for z/OS Solutions Information Center or DB2 Information Center for more details.

IMS or VSAM Replication: The average latency as reported by IMS or VSAM Replication may be higher than expected due to the following conditions:

  • Replication is restarted and there is a large amount of pending source updates to be processed. The average latency should return to a normal level when the backlog is processed.
  • The occurrence of a large high volume batch (BMP or Batch DL/I) window or a peak update period. The average latency should return to a normal level once the number of source updates to be processed has dropped and the servers have a chance to catch up.
  • Replication is started for a new subscription and the log position is set to a time in the distant past. Latency may appear artificially high, even though replication is working smoothly, since replication was started from an old log position.
    Suggested IMS or VSAM Replication user actions are:
  • Set the capture cache to 2G (the current max) and restart replication.
  • If the cache was already at 2G, you can let replication run, or if the subscription allows, consider increasing the apply PSB number for the subscription to increase parallelism. This may require IMS or VSAM pool space and DFSPZPxx member changes. Replication must be stopped to make this change. If the subscription does not qualify for parallel apply, consider creating 2 subscriptions, one with DBDs that qualify for parallel apply and another with the DBDs that do not qualify for parallel apply.

 

Copyright IBM Corp. 2011, 2013 All Rights Reserved US Government Users Restricted Rights - Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contact IBM