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 This column is obsolete and maintained for backward compatibility.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NEW	VARCHAR2(1)	Always set to N. This column is obsolete and maintained for backward compatibility.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

V$ACTIVE_SESS_POOL_MTH

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V$ACTIVE_SESS_POOL_MTH displays available active session pool resource allocation methods.

Column	Datatype	Description
NAME	VARCHAR2(40)	Name of the active session pool resource allocation method

Note:

1. select * from V$ACTIVE_SESS_POOL_MTH;

NAME

ACTIVE_SESS_POOL_ABSOLUTE

2. Views used to monitor resource manager usage include the following:

View	Description
DBA_RSRC_CONSUMER_GROUP_PRIVS USER_RSRC_CONSUMER_GROUP_PRIVS	DBA view lists all resource consumer groups and the users and roles to which they have been granted. USER view lists all resource consumer groups granted to the user.
DBA_RSRC_CONSUMER_GROUPS	Lists all resource consumer groups that exist in the database. Resource Manager system privileges. USER view lists all the users that are granted system privileges for the DBMS_RESOURCE_MANAGER package.
DBA_RSRC_MANAGER_SYSTEM_PRIVS USER_RSRC_MANAGER_SYSTEM_PRIVS	DBA view lists all users and roles that have been granted Database
DBA_RSRC_PLAN_DIRECTIVES	Lists all resource plan directives that exist in the database.
DBA_RSRC_PLANS	List all resource plans that exist in the database.
DBA_USERS USERS_USERS	DBA view contains information about all users of the database. Specifically, for the Database Resource Manager, it contains the initial resource consumer group for the user. USER view contains information about the current user, and specifically, for the Database Resource Manager, it contains the current user's initial resource consumer group.
V$ACTIVE_SESS_POOL_MTH	Displays all available active session pool resource allocation methods.
V$PARALLEL_DEGREE_LIMIT_MTH	Displays all available parallel degree limit resource allocation methods.
V$QUEUEING	Displays all available queuing resource allocation methods.
V$RSRC_CONSUMER_GROUP	Displays information about active resource consumer groups. This view can be used for tuning.
V$RSRC_CONSUMER_GROUP_CPU_MTH	Displays all available CPU resource allocation methods for resource consumer groups.
V$RSRC_PLAN	Displays the names of all currently active resource plans.
V$RSRC_PLAN_CPU_MTH	Displays all available CPU resource allocation methods for resource plans.
V$SESSION	Lists session information for each current session. Specifically, lists the name of each current session's resource consumer group.

Oracle data dictionary views

Oracle dynamic performance views

V$ACTIVE_SERVICES

V$ACTIVE_SERVICES displays information about the active services in the database.

Column	Datatype	Description
SERVICE_ID	NUMBER	Service ID
NAME	VARCHAR2(64)	Name of the service
NAME_HASH	NUMBER	Service name hash
NETWORK_NAME	VARCHAR2(512)	Network name
CREATION_DATE	DATE	Creation date
CREATION_DATE_HASH	NUMBER	Creation date hash
GOAL	VARCHAR2(12)	Service workload management goal: · NONE · SERVICE_TIME · THROUGHPUT
DTP	VARCHAR2(1)	Indicates whether the service is for DTP or distributed transactions including XA transactions (Y) or not (N)
BLOCKED	VARCHAR2(3)	Indicates whether a service on the specified instance is blocked from accepting new connections altogether (YES) or not (NO). If a service is blocked, then all connections will be directed to other instances (if any) that are hosting the desired service.
AQ_HA_NOTIFICATION	VARCHAR2(3)	Indicates whether AQ notifications are sent for HA events (YES) or not (NO)
CLB_GOAL	VARCHAR2(5)	Connection load balancing goal used with statistics that are sent to the listeners to determine how new connections are distributed: · LONG · SHORT

Note:

1.

select * from V$ACTIVE_SERVICES;

SERVICE_ID	NAME	NAM_ HASH	NETWORK_ NAME	CREATION_ DATE	CREATION_ DATE_ HASH	GOAL	DTP	BLOCKED	AQ_ HA_ NOTIFICATION	CLB_ GOAL
3	mydbXDB	1119650025	mydbXDB	2006-06-10 11:46:21 AM	168918946	NONE	N	NO	NO	LONG
4	mydb.env.gov.bc.ca	720991384	mydb.env.gov.bc.ca	2006-06-10 11:46:21 AM	168918946	NONE	N	NO	NO	LONG
1	SYS$BACKGROUND	165959219		2006-06-10 9:31:34 AM	0	NONE	N	NO	NO	SHORT
2	SYS$USERS	3427055676		2006-06-10 9:31:34 AM	18489460	NONE	N	NO	NO	SHORT

Oracle data dictionary views

Oracle dynamic performance views

V$ACTIVE_INSTANCES

V$ACTIVE_INSTANCES displays the mapping between instance names and instance numbers for all instances that have the database currently mounted.

Column	Datatype	Description
INST_NUMBER	NUMBER	Instance number
INST_NAME	VARCHAR2(60)	Instance name

Note:

1. This view is ONLY populated in Real Application Clusters mode (or in Parallel Server mode in Oracle8i and earlier).

Oracle data dictionary views

Oracle dynamic performance views

V$ACCESS

V$ACCESS displays information about locks that are currently imposed on library cache objects. The locks are imposed to ensure that they are not aged out of the library cache while they are required for SQL execution.

Column	Datatype	Description
SID	NUMBER	Session number that is accessing an object
OWNER	VARCHAR2(64)	Owner of the object
OBJECT	VARCHAR2(1000)	Name of the object
TYPE	VARCHAR2(24)	Type identifier for the object

Note:

1. Use the following script (Metalink note 1020010.6) to report the SQL text of some of the locks currently being held in the database.

select s.username username, a.sid sid, a.owner||'.'||a.object object, s.lockwait, t.sql_text SQL from v$sqltext t, v$session s, v$access a where t.address=s.sql_address and t.hash_value=s.sql_hash_value and s.sid = a.sid and a.owner != 'SYS' and upper(substr(a.object,1,2)) != 'V$';

Oracle data dictionary views

Oracle dynamic performance views