Troubleshooting performance issues

This chapter describes potential problems and workarounds regarding declines in system performance. See the IBM® OMEGAMON® for Storage on z/OS®: Tuning Guide for general tuning guidelines.

Data set I/O collection tuning
Performance of the Tivoli Data Warehouse database is degraded or there are gaps where historical data is unavailable for a specified collection period
A number of symptoms indicate that your database or persistent datastore is in need of maintenance. You might, for example, note that your DB2® transaction logs are filling up. You might see gaps in the data in the middle or at the end where no historical data is available for a specified collection period. This problem also manifests itself as degraded performance, such that database inserts require an unusually long period of time. Inserts must be completed between display intervals. Operations need to completed before the next collection interval to prevent the persistent data store from wrapping.
Long response times or no results returned when specifying historical collection time spans for some workspaces
For historical data collection in large data sets, the intervals that you set for refreshing historical workspaces, for data collection, and for data chunking can affect performance dramatically. For example, when you select a time span of many hours (for example, 24 hours) for a workspace where a large number (tens of thousands) of rows of data has been stored in the persistent data store, the resulting query can take 60 seconds or longer to complete. Also, the monitoring agent might use a high percentage of available CPU while the query is processed.