Rockwell Automation RSBizWare Administration Guide - Manual (Page 275)

Data compression Appendix C
If the data cannot reach the database server, the Data Compression
service caches its data on the local hard disk until the database
becomes available. When the database becomes available again, the
data is automatically sent to the database and the cache files are
purged.
If you view the Windows Task Manager or Service Control Panel,
you may notice the Data Compression service running even though
your FactoryTalk Transaction Manager configuration is stopped.
Do not manually shut down any compression services. If the services
are shut down manually, the data may not be written to the database
until the configuration is started again.
Rockwell Automation Publication BZWARE-IN001M-EN-P-June 2014 275