Working Offline: Using a Local Repository 
Purpose
Since BAPI and RFC metadata does not change often, you may be able to work with BAPI and RFC metadata which you have previously downloaded from an actual R/3 system. This allows you to work offline, meaning that you work with data in a local repository. This speeds your access to the data.
You can create multiple local repositories, each containing a different set of metadata.
A SAP Assistant local repository file uses the file type SDB.
Process Flow
To work with a local repository you must first save some metadata into a local repository file. You copy this data from an R/3 system.
You may
delete items from a local repository.You may also delete a local repository file, by deleting the SDB file in Windows.