The RMU Convert command operates by creating a converted copy of
    the system tables and indexes. This implies that the RDB$SYSTEM
    storage area might grow during the conversion, but it is unlikely
    that the system tables will be fragmented by the conversion
    process.

    Because a copy of the system tables is made, the time taken by
    the conversion is proportional to the amount of storage allocated
    to the system tables, or the number of rows in system tables, or
    both. This is typically a few minutes per database. However, if
    the database has very large system tables, the conversion can be
    costly. If the database has a large number of versions of some
    tables, it might be more efficient for you to use the SQL EXPORT
    and IMPORT statements to convert the database.

    After the conversion, both copies of the system tables are stored
    in the database. The Commit qualifier selects the converted copy
    and deletes the original copy. The Rollback qualifier selects the
    original copy and deletes the converted copy. You can specify
    either the Commit or the Rollback qualifier at a later time
    if you selected the Nocommit qualifier when the database was
    converted. Be aware that as long as Commit or Rollback are not
    selected after a Nocommit conversion, extra space will be taken
    up in the database to store both versions of the metadata. It
    is important to issue the Convert/Commit command after you have
    verified that the conversion was successful. (RMU will not let
    you convert to a newer version if the previous Convert was never
    committed, even if it was years ago.)

    While both copies of the system tables exist, the database is
    usable under Oracle Rdb release 7.2, but not under the earlier
    version. Also, DDL (data definition language) operations to the
    database are prohibited to ensure that both copies of the system
    tables remain consistent. After you specify either the Commit or
    the Rollback qualifier, you can again perform DDL operations on
    the database.

    If you convert a multifile database created prior to Oracle Rdb
    Version 6.1 by using the RMU Convert command with the Nocommit
    qualifier and then use the RMU Convert command with the Rollback
    qualifier to revert to the prior database structure level,
    subsequent verify operations might return an RMU-W-PAGTADINV
    warning message. See the Usage_Notes help entry under this
    command for details.