V$BH

V$BH displays the status and number of pings for every buffer in the SGA. This is a Real Application Clusters view.

Column	Datatype	Description
FILE#	NUMBER	Datafile identifier number (to find the filename, query DBA_DATA_FILES or V$DBFILE)
BLOCK#	NUMBER	Block number
CLASS#	NUMBER	Class number
STATUS	VARCHAR2(6)	Status of the buffer: · free - Not currently in use · xcur - Exclusive · scur - Shared current · cr - Consistent read · read - Being read from disk · mrec - In media recovery mode · irec - In instance recovery mode
XNC	NUMBER	Number of PCM x to null lock conversions due to contention with another instance. This column is obsolete and maintained for backward compatibility.
LOCK_ELEMENT_ADDR	RAW(4 | 8)	Address of the lock element that contains the PCM lock that is covering the buffer. If more than one buffer has the same address, then these buffers are covered by the same PCM lock.
LOCK_ELEMENT_NAME	NUMBER	The address of the lock element that contains the PCM lock that is covering the buffer. If more than one buffer has the same address, then these buffers are covered by the same PCM lock.
LOCK_ELEMENT_CLASS	NUMBER	The address of the lock element that contains the PCM lock that is covering the buffer. If more than one buffer has the same address, then these buffers are covered by the same PCM lock.
FORCED_READS	NUMBER	Number of times the block had to be reread from the cache because another instance has forced it out of this instance's cache by requesting the lock on the block in exclusive mode
FORCED_WRITES	NUMBER	Number of times GCS had to write this block to cache because this instance had used the block and another instance had requested the lock on the block in a conflicting mode
DIRTY	VARCHAR2(1)	Y - block modified
TEMP	VARCHAR2(1)	Y - temporary block
PING	VARCHAR2(1)	Y - block pinged
STALE	VARCHAR2(1)	Y - block is stale
DIRECT	VARCHAR2(1)	Y - direct block
NEW	VARCHAR2(1)	Always set to N. This column is obsolete and maintained for backward compatibility.
OBJD	NUMBER	Database object number of the block that the buffer represents
TS#	NUMBER	Tablespace number of block

Note:

1. select * from V$BH WHERE FILE#=16;

FILE#

BLOCK#

CLASS#

STATUS

XNC

FORCED_ READS

FORCED_ WRITES

LOCK_ ELEMENT_ ADDR

DIRTY

TEMP

PING

STALE

DIRECT

NEW

OBJD

TS#

16

3

12

xcur

0

0

0

00

N

N

N

N

N

N

4294967295

16

16

2

13

xcur

0

0

0

00

N

N

N

N

N

N

4294967295

16

2. V$BH shows the contents of the data buffers as well as the number of blocks for each type of segment in the buffer. It is especially useful for showing the amount of table and index caching in databases with multiple data buffer pools. The following script taken from Inside the Oracle data buffer cache analyzes the contents of data buffers.

set pages 999 set lines 92 ttitle 'Contents of Data Buffers' drop table t1; create table t1 as select o.owner owner, o.object_name object_name, o.subobject_name subobject_name, o.object_type object_type, count(distinct file# || block#) num_blocks from dba_objects o, v$bh bh where o.data_object_id = bh.objd and o.owner not in ('SYS','SYSTEM') and bh.status != 'free' group by o.owner, o.object_name, o.subobject_name, o.object_type order by count(distinct file# || block#) desc ; column c0 heading "Owner" format a12 column c1 heading "Object|Name" format a30 column c2 heading "Object|Type" format a8 column c3 heading "Number of|Blocks in|Buffer|Cache" format 99,999,999 column c4 heading "Percentage|of object|blocks in|Buffer" format 999 column c5 heading "Buffer|Pool" format a7 column c6 heading "Block|Size" format 99,999 select t1.owner c0, object_name c1, case when object_type = 'TABLE PARTITION' then 'TAB PART' when object_type = 'INDEX PARTITION' then 'IDX PART' else object_type end c2, sum(num_blocks) c3, (sum(num_blocks)/greatest(sum(blocks), .001))*100 c4, buffer_pool c5, sum(bytes)/sum(blocks) c6 from t1, dba_segments s where s.segment_name = t1.object_name and s.owner = t1.owner and s.segment_type = t1.object_type and nvl(s.partition_name,'-') = nvl(t1.subobject_name,'-') group by t1.owner, object_name, object_type, buffer_pool having sum(num_blocks) > 10 order by sum(num_blocks) desc ;

Oracle data dictionary views

Oracle dynamic performance views