Clarification - Catalog Folder on Media Server

I have a question regarding the files found in the Catalog folder (C:\Program Files\Symantec\Backup Exec\Catalogs).  The files are taking up too much space on the server.  I'm thinking of reducing the truncate period and the removal period.  Before I do that, I want to better understand what these files are used for.  If these files are removed that does that mean I'll loose my 9+ months of data showing me what data is on what tape (in the restore option)?