These files cache the database schema information so we can access it quickly.
The cache/index is only required for the SQL Editor error checking , quick fixes and type ahead not for database profiling or SQL Tuning.
I generally turn off this option in DB Optimizer. When connecting to a data source DB Optimizer will ask if the user wants to index/cache the schema. I suggest choosing “no”.
Once it is turned on, it can be turned off by going to menu “Window -> Preferences” and unchecking the “Enable Indexing” option:
We will be working on making the cache more efficient, smaller and on demand (ie only things actually being used) in the next release.