Call SOR$RELEASE_REC to pass records to SORT or MERGE with the
    record interface. SOR$RELEASE_REC must be called once for each
    record to be sorted.

    Some of the following condition values are used with different
    severities, depending on whether SORT/MERGE can recover. Thus,
    if you want to check for a specific status, you should use
    LIB$MATCH_COND.