A MDB can contain up to 1000 DBs, and any number of the 1000 DBs can be described as current and accessed at one time. Databases which cannot be accessed are described as non-current or deferred.

EXCHANGE replaces a current DB by a non-current DB. The DB names do not need to be listed in a particular order, since the MDB knows which are current and which are non-current, but they must be paired correctly if more than two names are listed.

CURRENT includes the specified DB at a given position in the Current list.

DEFER removes the specified DB from the Current list and makes it non-current.

For example, assume that an MDB contains the following DBs as shown by a LIST command:

after the EXCHANGE command is to insert the named DBs at positions 1 and 4 respectively in the Current list, resulting in

Note that the position specified for each DB to be added to the Current list applies after the previous insertions have been made.