Cache hash chains
- From: "Paul Harrison" <cure@xxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 3 Mar 2015 15:50:05 -0600
Hi Team,
The query below returns 4 rows. The database object BUFFCACHETEST has 4
database buffer headers(doubled linked list) attached to a hash bucket? Why do
we have 4 database buffer headers linked to 1 working data set( database buffer
cache block )?
select HLADDR, decode(STATE,0,'free',1,'xcur',2,'scur',3,'cr',
4,'read',5,'mrec',6,'irec',7,'write',8,'pi', 9,
'memory',10,'mwrite',11,'donated', 12,'protected',
13,'securefile', 14,'siop',15,'recckpt', 16,
'flashfree', 17, 'flashcur', 18, 'flashna') as STATE,
PRV_HASH, NXT_HASH,
BA, DBARFIL, DBABLK
from X$BH where OBJ = 78451 and DBABLK = 196393;
##
update BUFFCACHETEST set NUM=13 where NUM=3;
HLADDR STATE PRV_HASH NXT_HASH BA
---------------- ---------- ---------------- ---------------- ----------------
DBARFIL DBABLK---------- ----------
000000007A3E3548 xcur 000000007A3E38E8 0000000066FD2FF0 0000000066F04000
1 196393
000000007A3E3548 cr 0000000066FD2EA8 0000000066FD3138 0000000066F06000
1 196393
000000007A3E3548 cr 0000000066FD2FF0 0000000068FB7C50 0000000066F08000
1 196393
HLADDR STATE PRV_HASH NXT_HASH BA
---------------- ---------- ---------------- ---------------- ----------------
DBARFIL DBABLK---------- ----------
000000007A3E3548 cr 0000000066FD3138 000000007A3E38E8 0000000068C5E000
1 196393
Thanks,
Paul
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