Our database has grown significantly and our DBA has spotted that data in the NAS Transaction Log (NAS_TRANSACTION_LOG table) does not seem to be being trimmed according to the rules set in the Data_Engine. Assuming we don't want the data is it safe for the DBA to remove, 2015 -2017 data??
In this situation no changes are required to the data_engine settings. The NAS_TRANSACTION_LOG table is managed by the NIS BRIDGE settings. These tables are maintained by the nas using the NiS bridge configuration data. To keep the size of these tables in the NiS database manageable, they are automatically compressed at the configured administration interval, see the following documentation for more details:
The NiS Bridge Tab - https://docops.ca.com/ca-unified-infrastructure-management-probes/ga/en/alphabetical-probe-articles/nas-alarm-server/nas-im-configuration/the-nas-setup-tab#ThenasSetupTab-TheNiSBridgeTab
We've seen previously if the volume of data is large and the maintenance job cannot complete within the scheduled time frame, it will cancel the maintenance job and not delete any data. That could be the case here, if you manually delete the unwanted data from the NAS_TRANSACTION_LOG we would recommend taking a backup of the UIM database or table prior to removing the data (if possible) and stopping (deactivating) the data_engine and nas probes.
Regarding data_engine retention settings I would advise reviewing the following articles and best practices:
data_engine best practices - https://comm.support.ca.com/kb/dataengine-best-practices/kb000033592
How does data_engine handle retention? - https://comm.support.ca.com/kb/how-does-dataengine-handle-retention/kb000045990
How does data_engine maintenance and retention work? - https://comm.support.ca.com/kb/how-does-dataengine-maintenance-and-retention-work/kb000033704