--Check for GC Block Corruption-
SELECT
A.VALUE "GC BLOCKS LOST 1",
B.VALUE "GC BLOCKS CORRUPT 1",
C.VALUE "GC BLOCKS LOST 2",
D.VALUE "GC BLOCKS CORRUPT 2"
FROM GV$SYSSTAT A, GV$SYSSTAT B, GV$SYSSTAT C, GV$SYSSTAT D
WHERE A.INST_ID=1 AND A.NAME='gc blocks lost'
AND B.INST_ID=1 AND B.NAME='gc blocks corrupt'
AND C.INST_ID=2 AND C.NAME='gc blocks lost'
AND D.INST_ID=2 AND D.NAME='gc blocks corrupt';


--Check for lost GC Blocks
SELECT A.INST_ID "INSTANCE", A.VALUE "GC BLOCKS LOST",
B.VALUE "GC CUR BLOCKS SERVED",
C.VALUE "GC CR BLOCKS SERVED",
A.VALUE/(B.VALUE+C.VALUE) RATIO
FROM GV$SYSSTAT A, GV$SYSSTAT B, GV$SYSSTAT C
WHERE A.NAME='gc blocks lost' AND
B.NAME='gc current blocks served' AND
C.NAME='gc cr blocks served' and
B.INST_ID=a.inst_id AND
C.INST_ID = a.inst_id;