Parameters that change the characteristics of database storage
    area files. You can specify the same storage area parameters for
    either single-file or multifile databases, but the effect of the
    clauses in this part of an ALTER DATABASE statement differs.

    o  For single-file databases, the storage area parameters
       change the characteristics for the single storage area in
       the database.

    o  For multifile databases, the storage area parameters change
       the characteristics of the RDB$SYSTEM storage area.

       You can also change some of the characteristics of the
       RDB$SYSTEM storage area using the ALTER STORAGE AREA clause.
       However, you can only change the read-only and read/write
       parameters in this part of the ALTER DATABASE statement. See
       the ALTER_STORAGE_AREA topic in this Arguments list for more
       information about the RDB$SYSTEM characteristics that you are
       allowed to alter.

    The ALTER DATABASE statement does not let you change all storage
    area parameters you can specify in the CREATE DATABASE statement.
    You must use the EXPORT and IMPORT statements to change the
    following database root file parameters:

    o  INTERVAL

    o  PAGE FORMAT

    o  PAGE SIZE

    o  SNAPSHOT FILENAME

    o  THRESHOLDS