When you have worked with the main TM (translation memory) and the main TDB (terminology database) for a long time, these databases can become quite large. Especially when you want to copy a TM or TDB or to store them on media other than hard disks, it is recommended to compress them beforehand.
To compress the main TM, click on the menu command: MetaTexis | Translation memory (TM) | Compress main TM.
To compress the main TDB, click on the menu command: MetaTexis | Terminology database (TDB) | Compress main TDB.