Performance Tuning :: SID Column In V$SESSION?
Dec 12, 2010Even though the users are not logged in why the V$SESSOIN shows the SID and why many times?
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Performance Tuning :: Looking For More Than Last 16 Operations For Session
May 25, 2010Doing some data conversion at the moment and using V$SESSION_LONGOPS to predict when the current task will be finished so I can run the next one.
V$SESSION_LONGOPS seems to have only the last 16 long operations for the session. Older operations are automatically purged. My bigger tables have 32 partitions, so after the first 16 are processed, I cannot tell which partition I am up to.
Googling "old longops" and "longops history" didn't work, nor did the same searches on this site. The Oracle Reference manual section on V$SESSION_LONGOPS did not mention that older entries are purged.
Performance Tuning :: TKPROF Output For Session
Jun 9, 2010understanding the TKPROF output for the session that was executing an insert statement(inserting 70 lakh data) on which a row level trigger get fired and select from following table.The trace was run for 1 hour.
Table name - > GS_MAP_RCC_CCIT
This table is having 37 rows as in on single block and having primary key index on RCC_NUM that is also contained on single block.We are getting maximum wait events on db_file_sequential_read.
As per my understanding this is due to the contention for the same block because for each row these queries get fired.
Performance Tuning :: Session Doing FTS Not Appearing In Longops?
Apr 4, 2012dbo is a table with 1M records and structure similar to dba_objects
The following queries which does FTS, access same number of blocks as observed in v$session_longops
select * from dbo;
and
select * from dbo where object_type='VIEW';
Ex.
select * from dbo where object_type='VIEW';
select * from table(dbms_xplan.display_CURSOR(null,null,'ALLSTATS LAST'));
PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------
------------------------------------------------------------------------------
SQL_ID 5mh418w9stax2, child number 0
-------------------------------------
select * from dbo where object_type in('VIEW')
Plan hash value: 2675347415
-------------------------------------------
| Id | Operation | Name | E-Rows |
-------------------------------------------
|* 1 | TABLE ACCESS FULL| DBO | 77611 |
-------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("OBJECT_TYPE"='VIEW')
I understand that because the query is accessing large number of blocks which exceeds 6 seconds threshold, the session appears in v$session_longops And this has nothing to do with the time spent in displaying the records on the screen
Now, why the following query does not appear in v$session_longops?
select /*+ full(dbo) */ count(*) from dbo;
select /*+ full(dbo) */ count(*) from dbo;
COUNT(*)
----------
1006525
Elapsed: 00:00:01.36
dv3_erie-dev_08 >select * from table(dbms_xplan.display_CURSOR(null,null,'ALLSTATS LAST'));
PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------
SQL_ID 4mgjwp3tv70db, child number 0
-------------------------------------
select /*+ full(dbo) */ count(*) from dbo
Plan hash value: 1423969929
--------------------------------------------
| Id | Operation | Name | E-Rows |
--------------------------------------------
| 1 | SORT AGGREGATE | | 1 |
| 2 | TABLE ACCESS FULL| DBO | 1007K|
--------------------------------------------
The table has all nullable columns and thus I assume the index on ID can't be used for this COUNT Thus ideally it shall be accessing same number of blocks and thus shall appear in v$session_longops
Performance Tuning :: How To Set Commit_write Parameter To (BATCH) In Another Session
May 16, 2013How to set commit_write parameter to 'BATCH' in another session.
View 3 Replies View RelatedPerformance Tuning :: Session Tracing For Shared Servers
Jan 12, 2011How to enable tracing for sessions connected using shared servers ?
View 1 Replies View RelatedPerformance Tuning :: How To Trace Different Session From Current With LEVEL 4
Jun 13, 2012I've been searching the web for examples of how to run a trace.It's needed for a session different then current in trace LEVEL 4 (I need the bind variables values in the trace).
Unfortunately, I couldn't trace with DBMS_SUPPORT.START_TRACE_IN_SESSION, I understand that this is because it was only introduced in Oracle 11g.
how can i trace a session in level 4 on Oracle 10g for another session?
Performance Tuning :: SQL ID And Text - No Record Being Found At Session Level
Feb 22, 2012At my prod instance one sql query ran for about 9 hours.Now the sql query completed with success.Suddenly our ops team want to know the which sql query was running for 9 hours.As the query got success no record is being found at session level.
I know the SID.How Do I get the SQL query ?
Performance Tuning :: How To Find Out Session Consuming High Resource In Past
Mar 28, 2013How can I find out the particular oracle session which was consuming high memory in the past?
I can't get the data in v$sessstat
Unable to get the information in AWR
dba_hist_active_session_history do not have field which indicate memory related information
Shall I concetrate on EVENT in dba_hist_active_session_history which continuosly had sort, direct path read
Or
Locate sql_id from dba_hist_sqlstat with high SORTS_DELTA for snapshots belonging to problematic time period and then using the sql_id query dba_hist_active_session_history
which approach I shall take to find out the session which consumed most memory in the past?
Performance Tuning :: How Length Of Column Width Effects Index Performance
Sep 30, 2010How the length of column width effects index performance?
For example if i had IOT table emp_iot with columns:
(id number,
job varchar2(20),
time date,
plan number)
Table key consist of(id, job, time)
Column JOB has fixed list of distinct values ('ANALYST', 'NIGHT_WORKED', etc...).
What performance increase i could expect if in column "job" i would store not names but concrete numbers identifying job names.
For e.g. i would store "1" instead 'ANALYST' and "2" instead 'NIGHT_WORKED'.
Performance Tuning :: Efficient Way To Alter Column For TDE?
Jul 4, 2013I am using 11.2.0.3.0 version of oracle.
Now we are supposed to apply column level TDE to some of our table in database. Now it will be a 'ALTER' on the columns. it involves 4 big tables out of which 3 tables having size ~30GB(one is partitioned table) and another one ~800GB(Not partitioned) Now the concern is, what will be the efficient/safest way to apply TDE on columns, below are the two options with us. (NOTE - We do have downtime window during DB maintenance but looking at the size of the table, i suspect it might take lot.)
1. Directly apply 'ALTER' on the columns. (Note- i was testing on my local, it took 3hrs for a 30GB table to ALTER the column to TDE)
2. Use Table Redefinition for Altering the column. (Creating interim table with column as TDE and then Redefining whole table).
Performance Tuning :: Derived Column Index
Apr 2, 2011here is my query
SELECT CURRENTSTEP
FROM (SELECT ( WFENTRY.NAME
|| ','
|| CURRENTSTEP.STEP_ID
) AS CURRENTSTEP,
(CASE
WHEN WFENTRY.NAME IN
[Code]...
in this query I am concatenating tow columns , I use this query as a sub query in my other queries and filter the results with and CURRENTSTEP = ?
here is how I use it
select
sys_audit_id
from
( SELECT
*
FROM
(SELECT
F.FINDING_NUMBER,
[Code]....
I saw adding this as a subquery with the filter and CURRENTSTEP = ? is slowing my query very much , as this is a derived column i cannot add index then how to improve performance for this subquery ?
Performance Tuning :: Index Creation On Text Column?
Oct 10, 2013We have a table called address and having the address fields and city ,state etc. The table will store huge amount of data .We need to query on the table. I would like to know how can we fasten the query and improve the performance of the query by creating index on these columns...Query is given below . note that the nullable columns can have data
SELECT *
FROM address
WHERE address1 = 'a'
[Code]....
Performance Tuning :: Materialized View With Nullable Column
Dec 29, 2011I have an issue in materialized view which has got one of the null able column and query on this column taking approximately 2 mins where as other indexed columns takes less than 10 sec.
Here is the summary
SQL> Select Count (1), Count (VAT_NO) From Mv_customer;
COUNT(1) COUNT(VAT_NO)
---------------------------------
2893561 1516
If an index is created on VAT_NO will that improve the performance. What kind of index can be created considering very less number of records has got VAT_NO
Performance Tuning :: Cannot Collect Top Frequency Histogram On Column?
Jul 23, 2013I'm trying to collect histograms for column COL_C of table TAB_A(150K records), So an index "BAD_IDX" will *not* be used in a query when the value is not selective.
This is my query:
SELECT COL_A, COL_B , COL_C , COL_D , COL_E , COL_F
FROM TAB_A
WHERE COL_A = 050
AND COL_B = 13012345
AND COL_C = 0
AND COL_D = 0
AND COL_D >= '07/23/2013 00:00:00'
ORDER BY COL_E ASC;
Now, I have index "BAD_IDX" on columns (COL_C, COL_E ).and the distribution of values looks like this:
select COL_C, count(*)
FROM TAB_A --very not selective for 0, selective for the rest, also no histogram
group by rollup(COL_C)
order by 2 desc;
and the result is 20k row long (20k distincts), So I'll post just the top part of it:
COL_CCOUNT(*)
-------------
158382
086356
695583772
623044169
659558964
680045564
689664263
[code]...
Now, the problem with the query was that "COL_B = 13012345" was the most selective predicate, And an index for it did not exist, so the index "BAD_IDX" is used, and is scanning 86k records (all the "0" value records for column COL_C)!
So, I created an index
Create index GOOD_IDX on TAB_A(COL_B) compute statistics;
However, that BAD_IDX index is still being used! I've thought that maybe it's because the lack of histograms for the column COL_C.I've also understood from documentation I've read that the suitable histogram type is TOP FREQUENCY, Because although I have 20k distincts here for the column COL_C, what does the difference is the 86k records of value 0.
I try to create histograms for the column:
BEGIN
DBMS_STATS.GATHER_TABLE_STATS (
ownname => 'ANDREY'
, tabname => 'TAB_A'
, method_opt => 'FOR COLUMNS COL_C'
);
END;
/
But then when I check - I see that
1. My query is still using the wrong index
2. My histogram is height-balanced and not FREQUENCY
select histogram from dba_tab_columns where table_name='TAB_A' and column_name='COL_C' and owner=user;
The result is:
HISTOGRAM
----------
HEIGHT BALANCED
What do I need to do in order to
1. Make my query use the correct index
2. Create a FREQUENCY histogram
Performance Tuning :: Query Not Hitting Index On Date Column
May 18, 2012I am working with following select clause:
select distinct S.ID ID
from
ods.hso_Scheduled H,
ods.SO_SCHEDULED S
where
S.insertion_date >= to_date('01-DEC-2011') and S.insertion_date < to_date('01-FEB-2012')
and H.ID=S.ID
Both the involved tables, HSO_SCHEDULED is having 15 million records and SO_SCHEDULED table is having 7 million records.
I have created following indexes on these tables:
Indexes on SO_SCHEDULED:
Index name Column name
SS_IDX1ID, SO_SUB_ITEM__ID
SS_IDX2INSERTION_DATE
SS_IDX3ID, INSERTION_DATE
SS_IDX4ID, SO_SUB_ITEM__ID, INSERTION_DATE
SO_SCHEDULED_ID_PKID
Indexes on HSO_SCHEDULED:
HSS_IDX1ID, SO_SUB_ITEM__ID, LAST_UPDATING_DATE
HSS_IDX2ID, LAST_UPDATING_DATE
HSS_IDX3ID
My problem is despite of having relevant indexes present, my query is not hitting them and hence the performance is very bad.
Explain Plan:
Execution Plan
----------------------------------------------------------
Plan hash value: 574170360
--------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 814K| 38M| | 9574 (1)| 00:02:15 | | | |
| 1 | PX COORDINATOR | | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10002 | 814K| 38M| | 9574 (1)| 00:02:15 | Q1,02 | P->S | QC (RAND) |
| 3 | HASH UNIQUE | | 814K| 38M| 185M| 9574 (1)| 00:02:15 | Q1,02 | PCWP | |
|* 4 | HASH JOIN | | 2653K| 124M| | 9564 (1)| 00:02:14 | Q1,02 | PCWP | |
| 5 | PX JOIN FILTER CREATE| :BF0000 | 814K| 22M| | 3903 (1)| 00:00:55 | Q1,02 | PCWP | |
| 6 | PX RECEIVE | | 814K| 22M| | 3903 (1)| 00:00:55 | Q1,02 | PCWP | |
| 7 | PX SEND HASH | :TQ10000 | 814K| 22M| | 3903 (1)| 00:00:55 | Q1,00 | P->P | HASH |
| 8 | PX BLOCK ITERATOR | | 814K| 22M| | 3903 (1)| 00:00:55 | Q1,00 | PCWC | |
|* 9 | TABLE ACCESS FULL| SO_SCHEDULED | 814K| 22M| | 3903 (1)| 00:00:55 | Q1,00 | PCWP | |
| 10 | PX RECEIVE | | 14M| 272M| | 5654 (1)| 00:01:20 | Q1,02 | PCWP | |
| 11 | PX SEND HASH | :TQ10001 | 14M| 272M| | 5654 (1)| 00:01:20 | Q1,01 | P->P | HASH |
| 12 | PX JOIN FILTER USE | :BF0000 | 14M| 272M| | 5654 (1)| 00:01:20 | Q1,01 | PCWP | |
| 13 | PX BLOCK ITERATOR | | 14M| 272M| | 5654 (1)| 00:01:20 | Q1,01 | PCWC | |
| 14 | TABLE ACCESS FULL| HSO_SCHEDULED | 14M| 272M| | 5654 (1)| 00:01:20 | Q1,01 | PCWP | |
--------------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("H"."ID"="S"."ID")
9 - filter("S"."INSERTION_DATE">=TO_DATE(' 2011-12-01 00:00:00', 'syyyy-mm-dd hh24:mi:ss') AND
"S"."INSERTION_DATE"<TO_DATE(' 2012-02-01 00:00:00', 'syyyy-mm-dd hh24:mi:ss'))
Performance Tuning :: Create Partitioned Table With Column Of LONG Or LONGRAW?
Nov 3, 2010the reason behind the below statements:
1) We cant create TABLE PARTITIONED on CLUSTER or INDEX on CLUSTER TABLE.
2) We cant create a partitioned table with the column of LONG or LONGRAW? (But how it could be possible with BLOB, CLOB?
Performance Tuning :: Index Usage In Order By Clause On Nullable Column
Jan 28, 2011I came across situation where a Nullable column is not using index for 'order by' clause. I added Not Null condition in the 'where' condition but it wasn't useful. I don't wanted to make composite index with not nullable column or with constant or modify column to 'Not Null'
So I carried out test cases and during which I found that in one case the sql statement does 'fast full scan' for data access but does not use index for 'order by' sorting
here are the steps
Initially I kept the column Nullable
SQL> create sequence s5;
Sequence created.
SQL> create table t5 as select s5.nextval id,a.* from dba_objects a where rownum<1001;
Table created.
SQL> set pages 100
SQL> select column_name,nullable from user_tab_columns where table_name='T5';
SQL> create index i5 on t5(id);
Index created.
SQL> exec dbms_stats.gather_table_stats(user,'T5',cascade=>true);
PL/SQL procedure successfully completed.
exit
SQL> alter session set events '10046 trace name context forever, level 12';
select *
from
t5 where id is not null order by id
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 16 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.01 0.00 0 16 0 1000
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5
Rows Row Source Operation
------- ---------------------------------------------------
1000 SORT ORDER BY (cr=16 pr=0 pw=0 time=4771 us)
1000 TABLE ACCESS FULL T5 (cr=16 pr=0 pw=0 time=1157 us)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 49.49 49.72
********************************************************************************
select /*+ index(t i5) */ *
from
t5 t where id is not null order by id
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 150 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.00 0.00 0 150 0 1000
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5
Rows Row Source Operation
------- ---------------------------------------------------
1000 TABLE ACCESS BY INDEX ROWID T5 (cr=150 pr=0 pw=0 time=5167 us)
1000 INDEX FULL SCAN I5 (cr=71 pr=0 pw=0 time=3141 us)(object id 4673065)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 69 0.00 0.00
SQL*Net message from client 69 22.89 28.04
Now I modified the 'id' column to Not Null
SQL> alter table t5 modify id not null;
SQL> set pages 100
SQL> select column_name,nullable from user_tab_columns where table_name='T5';
COLUMN_NAME N
------------------------------ -
ID N
OWNER Y
OBJECT_NAME Y
SUBOBJECT_NAME Y
OBJECT_ID Y
DATA_OBJECT_ID Y
OBJECT_TYPE Y
CREATED Y
LAST_DDL_TIME Y
TIMESTAMP Y
STATUS Y
TEMPORARY Y
GENERATED Y
SECONDARY Y
14 rows selected.
select *
from
t5 order by id
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.01 0 29 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 16 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.01 0.01 0 45 0 1000
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5
Rows Row Source Operation
------- ---------------------------------------------------
1000 SORT ORDER BY (cr=16 pr=0 pw=0 time=2398 us)
1000 TABLE ACCESS FULL T5 (cr=16 pr=0 pw=0 time=1152 us)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 37.74 37.91
********************************************************************************
select /*+ index(t i5) */ *
from
t5 t order by id
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 150 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.00 0.00 0 150 0 1000
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5
Rows Row Source Operation
------- ---------------------------------------------------
1000 TABLE ACCESS BY INDEX ROWID T5 (cr=150 pr=0 pw=0 time=4166 us)
1000 INDEX FULL SCAN I5 (cr=71 pr=0 pw=0 time=3142 us)(object id 4673065)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 8.28 8.45
select id
from
t5 order by id
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 68 0.00 0.00 0 6 0 1000
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 70 0.00 0.00 0 6 0 1000
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5
Rows Row Source Operation
------- ---------------------------------------------------
1000 SORT ORDER BY (cr=6 pr=0 pw=0 time=1342 us)
1000 INDEX FAST FULL SCAN I5 (cr=6 pr=0 pw=0 time=1093 us)(object id 4673065)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 68 0.00 0.00
SQL*Net message from client 68 1.88 1.89
Questions are
1) Why adding 'where id is not null wasn't enough for the index to get used in 'order by'?
2) While we got 'fast full scan' why index wasn't used for 'order by' clause?
3) Do we need the indexed column in where clause for being used in 'order by clause' too?
4) Do we need 'order by' clause if we are selecting only the indexed column with sequence generated values?
Performance Tuning :: Unable To Update Newly Added Column In Existing Table
May 21, 2013I am facing some challenge while running update query on newly added column in existing table.
Environment Details
Oracle 9i, version 9.2.0.6
Os Unix Aix 6.1
No of records in table : 12572770
Below are the step i followed.
1. In table testtablename, I have added new column COLUMNNAME29 with datatype VARCHAR2(8).
2. After adding the new column, i executed the update query to populate the data form COLUMNNAME1 to COLUMNNAME29.
3. The query is executed using COLUMNNAME24 in where clause, to drive query in index based.
SQL> desc testtablename
Name Null? Type
----------------------------------------- -------- ----------------------------
COLUMNNAME1 VARCHAR2(8)
COLUMNNAME2 CHAR(1)
COLUMNNAME3 CHAR(1)
COLUMNNAME4 VARCHAR2(8)
COLUMNNAME5 VARCHAR2(11)
[Code]...
Table altered.
SQL> select index_name, column_position, column_name from dba_ind_columns where table_name = 'TESTTABLENAME' order by index_name,column_position;
INDEX_NAME COLUMN_POSITION COLUMN_NAME
------------------------------ --------------- --------------------------------------------------
IDX_TESTTABLENAME 1 COLUMNNAME24
Problem faced & My analysis
1. The update query is hanging in database, it's not progressing (In single update, approximately 40000 records will get update)
2. No oracle error thrown in alert log or in session where the query being executed.
3. The event for the query is "db file sequential read".
4. When i update the newly added column COLUMNNAME29 with static value "1", the update completed successfully in few seconds.
5. Then i changed the static value to "1111" and executed the update statement, which result to query hanging in database.
6. I tried to update the existing column(COLUMNNAME1) in table with static value "1111", the update completed successfully.
Below are the queries completed successfully
Update Testtablename
Set Columnname29 = '1'
Where Columnname24 >= To_Date('01-12-2002 00:00:00', 'DD-MM-YYYY HH24:MI:SS' )
And Columnname24 < To_Date('01-01-2003 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
[Code]...
Below are the queries hanging in database
Update Testtablename
Set Columnname29 = Columnname1
Where Columnname24 >= To_Date('01-12-2002 00:00:00', 'DD-MM-YYYY HH24:MI:SS' )
And Columnname24 < To_Date('01-01-2003 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
Update Testtablename
Set Columnname29 = '1111'
Where Columnname24 >= To_Date('01-12-2002 00:00:00', 'DD-MM-YYYY HH24:MI:SS' )
And Columnname24 < To_Date('01-01-2003 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
Below is character set in database
SQL> select * from v$nls_parameters;
PARAMETER VALUE
---------------------------------------------------------------- ----------------------------------------------------------------
NLS_LANGUAGE AMERICAN
NLS_TERRITORY AMERICA
NLS_CURRENCY $
NLS_ISO_CURRENCY AMERICA
[Code]....
Performance Tuning :: Tools For Database Tuning And Instance Tuning
Jul 12, 2010Looking to understand the difference between instance tuning and database tuning.
What is the difference between these two tuning exercises? I understand that an instance is memory based structures (logical) where as database consists of physical structures.
However, how does one tune a database the physical structure? Does it have to do with file placements/block sizes etc. Would you agree that a lot of that is taken care by ASM now in 11g? What tools are required/available (third party as well as oracle supplied) for these types of tuning scenarios?
Performance Tuning :: Update Currency Column Of One Table Using Other Table Currency Column?
May 11, 2012I am trying to update currency column of one table using the currency column of other table using the following sql code.
update ODS.SO_ITEM OSI
set CURRENCY__CODE=(select currency__code from sa_sales.SO_ITEM SSI where SSI.ID=OSI.ID)
This update is taking taking a lot of time and is never ending.
should i create index on source table (SA_SALES.SO_ITEM) or on target table (ODS.SO_ITEM) ?
Performance Tuning :: Merge Statement Tuning For 100M Records In Table?
Oct 31, 2011I have two tables with 113M records in DWH_BILL_DET & 103M in prd_rerate_chg_que and Im running following merge query, which is running for 13 hrs to update records, which is quiet longer time.
SQL> explain plan for MERGE /*+ parallel (rq, 16) */
INTO DWH_BILL_DET rq
USING (SELECT rated_que_rowid,
detail_rerate_flag_code,
rerate_sel_key,
[code].....
Performance Tuning :: Fragmentation Can Reduce Performance In Query Times
Jun 16, 2010I have a question about database fragmentation.I know that fragmentation can reduce performance in query times. The blocks are distributed in many extents and scans process takes a long time. Oracle engine have to locate the address of the next extent..
I want to know if there is any system view in which you can check if your table or index has high fragmentation. If it's needed I will have to re-create, move or rebulid the table or index, but before I want to know if the degree of fragmentation is high.
Any useful script or query to do this, any interesting oracle system view?
Performance Tuning :: Method Of Tuning Database - Row Reduction?
Oct 20, 2010There is a simple way to increase the performance of a query by reducing the row-size of the table it hits. I used it in the past by dividing the table into smaller parts and querying respective smaller table in each query.
what is this method called ? just forgot the method and can't recall it. what this type of row-reduction optimization is called ?
Performance Tuning :: Performance Standard Edition Without Partitioning?
Jun 16, 2011How many records could I have in a single table without performance degradation with Standard Edition without partitioning with cutting-edge server (8 or 12 cores, 72 GB RAM, FC 4 Gbit, etc...) and good storage?
300 Millions in only one table with 500K transactions / day is too much?
Simple database with simple schema.
How many records begin to be too many?
Performance Tuning :: Procedure Performance On New Database Import?
Nov 15, 2010Testing our 9i to 11g upgrade, we've imported the entire DB into the new machine.We've found that certain procedures are really suffering performance problems. BUT, we've also found, that if we check out a production copy of the procedure from our source code control, and reinstall it, the performance issue goes away. Just alter the procedure and recompiling does NOT work.
The new machine where the 11g database exists is slightly different than the source, but it's not like we have this problem with every procedure. It's only a couple.
any possible reason that we'd have to re-install a procedure to correct a performance problem?
Performance Tuning :: Checking Delete Performance In Package
Apr 12, 2013I need to check the package performance and need to improve the package performance.
1. how to check the package performance(each and every statement in the package)?
2. In the package using the delete statement to delete all records and observed that delete is taking long time to delete all the records in the table(Table records 7000000). This table is like staging table.Daily need to clean the data before inserting the data into it. what can I use instead of Delete.
Performance Tuning :: Query Performance Gain Using Statistics?
Aug 9, 2010Somewhere I read that we should not use hints in Oracle production environments, but we can use hints in the development environment and on achieving the desired execution plan we can adjust the 'statistics' to follow that plan without hints.
Q1. If it is true what statistics do we adjust for influencing the execution plan and how?
For example, I have the following simple query:
select e.empid, e.ename, d.dname
from emp e, dept d
where e.deptno=d.deptno;
emp.empid, emp.deptno and dep.deptno columns have indexes and the tables have the standard structure as found in the basic oracle examples.
If I look at the execution plan of the above query then I see that the driving table is empand the driven table is dept.Also the type of join that is taking place is 'Nested Loop'.
Questions: With respect to the above query,
Q 2. If I want to make dept the driving table and emp the driven table then how can I adjust the statistics to achieve that?
Q 3. If I want to use hash join instead of a nested loop join then then how can I adjust the statistics to achieve that?
I can put the ordered and the use_hash hint to effect this but again I have heard that altering statistics is a more robust way to control an execution plan as compared to hints.
Performance Tuning :: How To Improve The Performance Of Export Job (expdp)
Dec 6, 2011I have an issue with export(expdp).
When i exporting an user using expdp utility, the load the on the server is going up-to 5. The size of the database is 180GB. Below is the command that i use for export.
expdp sys/xxxx directory=dbpdump dumpfile=expdp_trk_backup.dmp logfile=expdp_trk_backup.log exclude=statistics schemas=trk
Do i need any look into any memory parameters for this?
Performance Tuning :: DECODE In WHERE CLAUSE Performance?
Oct 17, 2011The following query gets input parameter from the Front End application, which User queries to get Reports.There are many drop down boxes like LOB, FAMILY, BRAND etc., The user may or may not select values from drop down boxes.
If the user select any one or more values ( against each drop down box) it has to fetch all matching values from DB. If the user does'nt select any values it has to fetch all the records, in this case application will send a value 'DEFAULT' (which is not a value in DB ) so that the DB will fetch all the records.
For getting this I wrote a query like below using DECODE, which colleague suggested that will hamper performance.From the below query all the variables V_ are defined in procedure which gets the values selected by user as a comma separated string here V_SELLOB and LOB_DESC is column in DB.
DECODE (V_SELLOB, 'DEFAULT', V_SELLOB, LOB_DESC) IN
OPEN v_refcursor FOR
SELECT /*+ FULL(a) PARALLEL(a, 5) */
*
FROM items a
WHERE a.sku_status = 'A'
[code]...
