Applications that specify the database attach attribute DBKEY
    SCOPE IS ATTACH can accumulate locked space and locked dbkeys
    within the database. If one user is connected to the database in
    DBKEY SCOPE IS ATTACH mode, all users are forced to operate in
    this mode, even if they are explicitly connected in TRANSACTION
    mode. No dbkeys are reused until the ATTACH session disconnects.

    The RMU Reclaim command allows database keys of deleted rows to
    be rapidly reset in one or more storage areas. The RMU Reclaim
    command reads and updates all pages in a storage area, and, where
    possible, releases locked lines and locked free space so that
    they are available for later allocation.