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| Monday, August 3, 2009 |
| Data Dictionary Info |
Data Dictionary Info
Here are some scripts related to Data Dictionary Info .
Dictionary Cache
DATA DICTIONARY CACHE NOTES:
Parameter - Name of the parameter that determines the number of entries in the data dictionary cache.
Gets - Total number of requests for information on the data object.
Getmisses - Number of data requests resulting in cache misses.
% Cache Misses - Miss Ratio
Count - Total number of entries in the cache
Usage - Number of cache entries that contain valid data.
This report shows the DC cache statistics (a part of the shared pool). Whenever the database parses a SQL statement, it scans the text for syntax and semantic correctness. The semantic check requires cross-referencing of the information in the SQL statement and the data dictionary, including the table names, columns-to-date relationships, column names, data types, and security access privileges. To resolve the relationships, Oracle uses the data dictionary cache in the SGA. When the data sought in not in the cache, Oracle executes SQL statements to retrieve the data dictionary information from the SYSTEM tablespace. These statements for data dictionary information represent one type of recursive SQL statement. To increase the size available to the dictionary cache, increase the size of the shared pool area (via the SHARED_POOL_SIZE init.ora parameter.) Missing a get on the data dictionary or shared pool area of the SGA is more costly than missing a get on a data buffer or waiting for a redo buffer. If these parameters look familiar - you are probably recalling them from Oracle v6 (when you tuned these in the init.ora file)
select PARAMETER,
GETS,
GETMISSES,
round(GETMISSES/GETS,2)*100 "% Cache Misses",
COUNT,
USAGE
from v$rowcache
where GETS > 0
order by (GETMISSES/GETS)*100 desc
Latch Gets/Misses
LATCH GET AND MISS NOTES:
Latch Name - Name of the latch
Gets - Number of times obtained wait
Misses - Number of time obtained with wait but failed first try
Gets / Misses % - Ratio of misses to gets
Immediate Gets - Number of times obtained with no wait
Immediate Misses - Number of times failed to get with no wait
select NAME,
GETS,
MISSES,
round(((GETS-MISSES)*100) / GETS , 2) "Gets/Misses %",
IMMEDIATE_GETS,
IMMEDIATE_MISSES
from v$latch
where GETS != 0
or IMMEDIATE_MISSES > 0
order by ((GETS-MISSES) / GETS) descLabels: Data Dictionary Info |
posted by Srinivasan .R @ 11:37 PM  |
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| Redo Log Buffer |
Redo Log Buffer
Here are some scripts related to Redo Log Buffer .
Contention
REDO LOG CONTENTION NOTES:
Redo Latch Name - Name of the latch
Gets - Number of times gotten wait
Misses - Number of times gotten wait but failed first try
Sleeps - Number of times slept when wanted wait
Immediate Gets - Number of times gotten without wait
Immediate Misses - Number of times failed to get without wait
Heavy access to the redo log buffer can result in contention for redo log prompt buffer latches.
select NAME,
GETS,
MISSES,
SLEEPS,
IMMEDIATE_GETS,
IMMEDIATE_MISSES
from v$latch
where NAME in ('redo allocation','redo copy')
Statistics
REDO BUFFER NOTES:
Parameter - Name of the parameter
Value - Current value for the parameter
select NAME,
VALUE
from v$sysstat
where NAME like 'redo%'
and VALUE > 0Labels: Redo Log Buffer |
| posted by Srinivasan .R @ 11:24 PM |
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| Contention/Locking |
Contention/Locking
Here are some scripts related to Contention/Locking .
Lock Info
LOCK INFORMATION NOTES:
OS User - Name of operating system user
OS PID - Operating system process id
Oracle User - Name of Oracle user
Oracle ID - Oracle session id
Lock Type - Type of lock
Lock Held - Current lock held
Lock Requested - Type of lock requested
Status - Status of object (Blocking, Not Blocking, Global)
Object Owner - Owner of the object
Object Name - Name of the object
select OS_USER_NAME os_user,
PROCESS os_pid,
ORACLE_USERNAME oracle_user,
l.SID oracle_id,
decode(TYPE,
'MR', 'Media Recovery',
'RT', 'Redo Thread',
'UN', 'User Name',
'TX', 'Transaction',
'TM', 'DML',
'UL', 'PL/SQL User Lock',
'DX', 'Distributed Xaction',
'CF', 'Control File',
'IS', 'Instance State',
'FS', 'File Set',
'IR', 'Instance Recovery',
'ST', 'Disk Space Transaction',
'TS', 'Temp Segment',
'IV', 'Library Cache Invalidation',
'LS', 'Log Start or Switch',
'RW', 'Row Wait',
'SQ', 'Sequence Number',
'TE', 'Extend Table',
'TT', 'Temp Table', type) lock_type,
decode(LMODE,
0, 'None',
1, 'Null',
2, 'Row-S (SS)',
3, 'Row-X (SX)',
4, 'Share',
5, 'S/Row-X (SSX)',
6, 'Exclusive', lmode) lock_held,
decode(REQUEST,
0, 'None',
1, 'Null',
2, 'Row-S (SS)',
3, 'Row-X (SX)',
4, 'Share',
5, 'S/Row-X (SSX)',
6, 'Exclusive', request) lock_requested,
decode(BLOCK,
0, 'Not Blocking',
1, 'Blocking',
2, 'Global', block) status,
OWNER,
OBJECT_NAME
from v$locked_object lo,
dba_objects do,
v$lock l
where lo.OBJECT_ID = do.OBJECT_ID
AND l.SID = lo.SESSION_ID
SQL Lock Info
SQL ASSOCIATED WITH LOCK NOTES:
Oracle User - Name of the oracle user
SID - Oracle session id
Serial# - Serial# of the process
Type - Resource type (RW - Row wait enqueue lock, TM - DML enqueue lock, TX - Transaction enqueue lock, UL - User supplied lock)
Held - Type of lock held
Requested - Type of lock requested
ID1 - Resource identifier #1
ID2 - Resource identifier #2
SQL - SQL statement
select sn.USERNAME,
m.SID,
sn.SERIAL#,
m.TYPE,
decode(LMODE,
0, 'None',
1, 'Null',
2, 'Row-S (SS)',
3, 'Row-X (SX)',
4, 'Share',
5, 'S/Row-X (SSX)',
6, 'Exclusive') lock_type,
decode(REQUEST,
0, 'None',
1, 'Null',
2, 'Row-S (SS)',
3, 'Row-X (SX)',
4, 'Share',
5, 'S/Row-X (SSX)',
6, 'Exclusive') lock_requested,
m.ID1,
m.ID2,
t.SQL_TEXT
from v$session sn,
v$lock m ,
v$sqltext t
where t.ADDRESS = sn.SQL_ADDRESS
and t.HASH_VALUE = sn.SQL_HASH_VALUE
and ((sn.SID = m.SID and m.REQUEST != 0)
or (sn.SID = m.SID and m.REQUEST = 0 and LMODE != 4 and (ID1, ID2) in
(select s.ID1, s.ID2
from v$lock S
where REQUEST != 0
and s.ID1 = m.ID1
and s.ID2 = m.ID2)))
order by sn.USERNAME, sn.SID, t.PIECELabels: Contention/Locking |
| posted by Srinivasan .R @ 11:20 PM |
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| Full Table Scans |
Full Table Scans
Here are some scripts related to Full Table Scans .
System Statistics (Table)SYSTEM STATISTICS (TABLE) NOTES:
Statistic Name - Name of the statistic
Bytes - Size
This query provides information on the full table scan activity. If your application is OLTP only, having long full table scans can be an indicator of having missing or incorrect indexes or untuned SQL.
Table fetch by rowid reflect the cumulative number of rows fetched from tables using a TABLE ACCESS BY ROWID operation.
Table fetch continued row reflect the cumulative number of continued rows fetched. This value is incremented when accessing a row that is longer than a block in length and when accessing "migrated" rows. Migrated rows are rows that were relocated from their original location to a new location because of an update that increased their size to the point where they could no longer be accommodated inside their original block. Access to migrated rows will cause this statistic's value to increment only if the access is performed by ROWID. Full table scans of tables that contain migrated rows do not cause this counter to increment.
Table scan blocks gotten reflect the cumulative number of blocks read for full table scans.
Table scans rows gotten reflect the cumulative number of rows read for full table scans.
Table scans (cache partitions) is used with the Parallel Query Option. The number of RowID ranges corresponds to the number of simultaneous query server processes that scan the table.
Table scans (long scans) indicate a full scan of a table that has > 5 database blocks.
Table scans (rowid ranges) is used with the Parallel Query Option. The number of RowID ranges corresponds to the number of simultaneous query server processes that scan the table.
Table scans (short scans) indicate a full scan of a table that has <= 5 database blocks.
select NAME,
VALUE
from v$sysstat
where NAME like '%table'
Process Table Scans
PROCESS TABLE SCAN NOTES:
User Process - Name of user process
Long Scans - Full scan of a table that has > 5 database blocks.
Short Scans - Full scan of a table that has <= 5 database blocks.
Row Retrieved - Cumulative number of rows read for full table scans.
select ss.username||'('||se.sid||') ' "User Process",
sum(decode(name,'table scans (short tables)',value)) "Short Scans",
sum(decode(name,'table scans (long tables)', value)) "Long Scans",
sum(decode(name,'table scan rows gotten',value)) "Rows Retreived"
from v$session ss,
v$sesstat se,
v$statname sn
where se.statistic# = sn.statistic#
and (name like '%table scans (short tables)%'
or name like '%table scans (long tables)%'
or name like '%table scan rows gotten%')
and se.sid = ss.sid
and ss.username is not null
group by ss.username||'('||se.sid||') '
Process Table Scans (Avg)
PROCESS TABLE SCAN (AVERAGE) NOTES:
User Process - Name of user process
Short Scans - Number of short scans (<= 5 blocks)
Long Scans - Number of long scans (> 5 blocks)
Rows Retrieved - Number of rows retrieved
Long Scans Length - Average long scan length (i.e. full table scan of > 5 blocks)
select ss.username||'('||se.sid||') ' "User Process",
sum(decode(name,'table scans (short tables)',value)) "Short Scans",
sum(decode(name,'table scans (long tables)', value)) "Long Scans",
sum(decode(name,'table scan rows gotten',value)) "Rows Retreived",
round((sum(decode(name,'table scan rows gotten',value)) - (sum(decode(name,'table scans (short tables)',value)) * 5)) / (sum(decode(name,'table scans (long tables)', value))),2) "Long Scans Length"
from v$session ss,
v$sesstat se,
v$statname sn
where se.statistic# = sn.statistic#
and (name like '%table scans (short tables)%'
or name like '%table scans (long tables)%'
or name like '%table scan rows gotten%')
and se.sid = ss.sid
and ss.username is not null
group by ss.username||'('||se.sid||') '
having sum(decode(name,'table scans (long tables)', value)) != 0
order by 3 descLabels: Full Table Scans |
| posted by Srinivasan .R @ 11:15 PM |
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