File server databases like Access/JET MDB and ACCDB files need to be periodically compacted and repaired for optimal performance and to minimize database corruption. This also eliminates database bloat that can occur as data is added and deleted in the database.
Microsoft Access databases can be manually compacted from the Access menu. Unfortunately, over the last few versions of Access, the location of this command has moved around driving Access many users and developers crazy. Read our paper on Microsoft Access Database Compact and Repair to Minimize Corruption and Avoid Bloat (by Access Version).