On the middleware server I see that the files Syntax_ID.data and Syntax_ID.indx are growing and growing.
What is the maximal size of these files?
The default size limit is set at 1,572,864 KB (1.5 GB). This file size should never be increased beyond the max limit up to 1,992,294 KB (1.9 GB).
These files hold ALL the SQL statements collected by the collector. When the monitored database runs many different SQLs, Syntax_ID.data can increase in size. Another reason can be if the fine granular time pyramid resolution data (such as 1 minute or 1 hour data) is retained for a longer time than defaults specified with in middleware.
Syntax_ID.data and Syntax_ID.indx are not log files and are crucial files required by PA to show SQL statements in PA GUI for a given history period. If you delete these files before the dimensions data as aggregated by middleware is pushed to repository, you will lose data in PA.