GV$RMAN_COMPRESSION_ALGORITHM definition in Oracle Database 11.2
GV$RMAN_COMPRESSION_ALGORITHM
SELECT
inst_id, -- INST_ID NUMBER
algname_krbmca, -- ALGORITHM_NAME VARCHAR2(64)
decode( -- INITIAL_RELEASE VARCHAR2(18)
lowvsn_krbmca, '', NULL, lowvsn_krbmca),
decode( -- TERMINAL_RELEASE VARCHAR2(18)
highvsn_krbmca, '', NULL, highvsn_krbmca),
algdesc_krbmca, -- ALGORITHM_DESCRIPTION VARCHAR2(64)
algvsn_krbmca, -- ALGORITHM_COMPATIBILITY VARCHAR2(18)
DECODE( -- IS_VALID VARCHAR2(3)
isvalid_krbmca, 0, 'NO', 'YES'),
DECODE( -- REQUIRES_ACO VARCHAR2(3)
bitand(flags_krbmca, 1), 0, 'NO', 'YES')
FROM
x$krbmca
WHERE
bitand(flags_krbmca, 2) = 0