Performance Tuning :: How Does Standard Versus Advanced Handle Index Compression
Aug 18, 2010How does standard vs advanced handle index compression? Is there an advantage to having one vs the other besides the incurred cost?
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Performance Tuning :: Local Index Versus Global Index On Partitioned Table
Jun 28, 2011I have a huge table (about 60 gb) partition over range. The index on this table is global index created on 4 columns together. I have a query which is running very slowly. The explain plan is showing the use of this global index.Explain plan is not showing pstart and pend because the index is global.
View 6 Replies View RelatedPerformance Tuning :: Create Versus Rebuild Index
Jan 27, 2011I was comparing cost of rebuild vs create index...I carried out the following test
SQL> create table t4 as select * from t1;
Table created.
SQL> create table t5 as select * from t1 where 1=2;
Table created.
SQL> create index i5 on t5(id);
Index created. SQL> select bytes,extents,blocks from user_segments where segment_name='I5';
BYTES EXTENTS BLOCKS
---------- ---------- ----------
65536 1 8
SQL> alter index i5 unusable;
Index altered.
SQL> alter table t5 nologging;
Table altered.
SQL> Alter session set skip_unusable_indexes=True;
Session altered.
SQL> insert /*+ append */ into t5 select * from t1;
563904 rows created.
SQL> commit;
Commit complete.
Now I compared the cost (elapsed time, logical I/O) of the operations
create index i4 on t4(id);
Vs
alter index i5 rebuild online;
Following is the related trace of above 2 steps
create index i4 on t4(id)
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 1 0 0
Execute 1 1.17 3.38 9497 7869 335 0
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 1.17 3.38 9497 7870 335 0
Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 5
[code]....
So which option we shall pick in such cases? {Of course I haven't set 'nologging' for the indices but it is same for both indices we are comparing}
Advanced Compression In Oracle 11g R2?
Aug 8, 2012Hybrid Columnar Compression is dependent on the underlying storage system. See Oracle Database Licensing Information for more information.
The below is from the Oracle® Database PL/SQL Packages and Types Reference
Compression Constant Compression Level Description
COMP_FOR_OLTP 2 OLTP compression
COMP_FOR_QUERY_HIGH 4 High compression level for query operations
COMP_FOR_QUERY_LOW 8 Low compression level for query operations
COMP_FOR_ARCHIVE_HIGH 16 High compression level for archive operations
COMP_FOR_ARCHIVE_LOW 32 Low compression level for archive operations
To use Compression Level 4 or higher do we have to have ZFS or Pillar storage ?
Text :: Advanced Compression And Oracle Tables / Indexes
Sep 11, 2012I have noticed that Oracle text related objects, particularily the $I tables are some of the largest objects in our database. I have been actively pursuing utilizing Oracle advanced compression in our databases for OLTP table compression and LOB object compression. I have been unable to find any documentation or notes on if it is advisable to implement either table OLTP or LOB compression for Oracle text objects.
View 1 Replies View RelatedPerformance 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 :: AWR Report In 11g Standard Not Supported?
Jan 15, 2011I was trying to generate AWR report, but the report which got generated consist most of the sections without data. Later i came to know that AWR report is not fully supported in 11g? Is that true?
View 6 Replies View RelatedPerformance Tuning :: Oracle Buffer Versus AIX Filesystem Cache
May 7, 2011I am currently in the favorable situation in which I have excess amounts of memory available on the database server - a single node setup. The server only serves the single instance and no other processing. Database size is around 2.3tb and memory is 50gb. For the majority of processing, AIX is allocating a significant amount (anywhere from 30-40%) of the memory to the AIX file system cache (persistent pages).
I've been trying to find documentation about this, but have not had any luck yet. My guess is that it would be better to allow Oracle to cache this data - meaning increase the SGA target and max size to allow for a larger buffer cache. However, the nice thing about the AIX cache is if process memory is needed, the file system cache gives up pages. If the memory was allocated to the SGA, its pretty much locked in.
I have read several articles stating that a larger buffer cache is not always better, as a larger cache takes more management. But having both of the caches active seem to be a waste of memory, effectively storing the data twice - once in AIX persistent pages and a second time in Oracle database buffer cache.
Performance Tuning :: Access Direct Table Versus View
Dec 9, 2011If you have 3 tables (yr09, yr10,yr11) one with 2009 data, 2010 and 2011 data respectively. And a view (vw_yr091011) with a "union all" on all three.
Question: Will the performance be same for the following two queries ?
Question: Will Oracle read all 3 tables in the view when we search for only one year ?
select count(*) from yr09
where year = 2009;
-- vs
select count(*) from vw_yr091011
where year = 2009;
The following link says yes, the performance remains the same.
Link: [URL]..........
when I tried on a volume of 14000 records. The count came out same but the view took 50 more sec. And the explain plan shows it accessed all three tables.
Performance Tuning :: Oracle10g Standard Edition On Linux Machine
Jan 16, 2012In my production ENV there is two node RAC database is running , and on both machine RAM size is (35GB on node1,41GB on Node2) and other configuration is like below.
SGA SGA_TARGET DB_BLOCK_SIZE DB_MULTIBLOCK_READ_COUNT
NODE1 16G 14G 8K 16K
NODE2 16G 14G 8K 16K
Our Database size is 700GB approx.
The above SGA configuration is ok or need to be increase the size of SGA , our HIT RATIO is almost 99%.
Performance Tuning :: Standard SQL Query To Benchmark Oracle DB Response Time?
Oct 26, 2013I wish to run a SQL query and measure elapsed time, then compare the values to other Oracle DBs from other companies. That will give me a feeling if our DB performs well.For example in UNIX world, you can create a random 4GB file to measure throughput I/O and compare the values (for example 4MB/sec).
What's the simplest way to compare DB response time from forum members to our own DB? I don't need 100% accurate numbers.
Performance Tuning :: How Expensive (speed) Is Unique Versus Primary Key In Large Table
Aug 15, 2011I have two design alternatives and need to understand how expensive (speed) is one of them against the other for a medium size table (100K-200K records):
create table xyz
(
f1 number not null,
f2 varchar2(20) not null,
f3 number not null,
f4 varchar2(50),
[code]....
the idea is to optimize the design by using a PK instead of the 3 keys and there is a debate that searching a unique index field(2nd scenario) is of the same speed than searching a PK field (1st scenario).
Performance Tuning :: Index With NVL / Query Is No Longer Using Index
Nov 19, 2010I have a query which had a join:
a.c1=b.c1 and a.c2=@var
where @var is user supplied input at runtime...We had a index on a.c2 . The CBO would use this index to generate an opitimised query plan.We found some records from table "b" were dropping due to inner join. So we made a change in join. It'd be like
a.c1(+)=b.c1 and nvl(a.c2,@var)=@var
This query is no longer using the index, instead its doing a full table scan causing the query to slowdown.I have tried creating index on nvl(a.c2,'31-dec-9999')
But the CBO won't use it.Anyway to create index on this col so that full table scan can be avoided?
Performance Tuning :: Force Index If Table Not Using Index?
Aug 9, 2013How to force an index if the table not using the index?
View 10 Replies View RelatedPerformance 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 :: SQL Not Using Index From Application?
Jun 6, 2013We have a DELETE statement when coming from application is not using index but when run from Toad or SQLplus as same user uses index. Explain plan also shows using index.I did a query on v$sql below is the output of the query( I have attached the same as a txt file). All the stats are up to date and confirmed from the developer the variable B1 is using the same datatype as column MAXMKY.
SQL_TEXTSQL_ID DISK_READSOPTIMIZER_HASH_VALUE
DELETE LOTA WHERE MAXMKY=:B1 2g2prrp3z56ah19,099,1891,846,735,884
DELETE LOTA WHERE MAXMKY=:B1 2g2prrp3z56ah0 1,846,735,884
OPTIMIZER_COST HASH_VALUEPLAN_HASH_VALUE MODULEPARSING_SCHEMA_NAME
[code].....
Performance Tuning :: STOPKEY And Index Use
Nov 6, 2010I am working on a query for a feedback response system which is going to be targeted at the common case when the user only want the most recent 10-20 rows in the feedback table. My though is to create an index on the date column, do a sort in an inner query and rownum <= in an outer query. This works as I expect when I am only querying the main table (lookup by index with a stop key), but when I start joining the main table to attribute tables I end up with a full table scan of the main table with the stop key applied after all the joins are completed, the index is nowhere to be found.
CREATE TABLE attr1_tbl(attr1_id NUMBER NOT NULL, attr1 VARCHAR2(10) NOT NULL,
CONSTRAINT attr1_pk PRIMARY KEY (attr1_id));
CREATE TABLE attr2_tbl(attr2_id NUMBER NOT NULL, attr2 VARCHAR2(10) NOT NULL,
CONSTRAINT attr2_pk PRIMARY KEY (attr2_id));
CREATE TABLE attr3_tbl(attr3_id NUMBER NOT NULL, attr3 VARCHAR2(10) NOT NULL,
CONSTRAINT attr3_pk PRIMARY KEY (attr3_id));
[code]....
One thing I noticed was that when no data is selected from the attribute tables, even if they are joined in the query, the CBO throws them out of the plan and only accesses the main table. With the foreign keys this makes sense and really just disqualified my first thought that maybe I was missing a foreign key or not null constraint somewhere.
I also added the cardinality hint to overcome the chance that in my test case there was so little data that index access is not worth it.
Performance Tuning :: How To Create Index
Mar 30, 2013I am going through this scenario:
* 35 | ID TABLE ACCESS BY INDEX ROW | S_ORG_EXT | 3064K| 2472M| | 1 (0)| 00:00:01 |
| 36 | INDEX FULL SCAN | S_ORG_EXT_U1 | 14 | | | 1 (0)| 00:00:01 |
Predicate Information (identified by operation id):
---------------------------------------------------
35 - filter("T2"."ACCNT_FLG"<>'N' AND ("T2"."INT_ORG_FLG"<>'Y' OR "T2"."PRTNR_FLG"<>'N'))
This unselective index scan on step 36 of the explain is returning 14 rows but optimizer is selecting 3064 K rows from the table .
I tried creating combined index on all 3 columns mentioned in the predicates for 35th step , but that is not utilized .
how to index this whole expression ::--
(ACCNT_FLG<>'N' AND (INT_ORG_FLG<>'Y' OR PRTNR_FLG<>'N'))
Something like CREATE INDEX XYZ on table((ACCNT_FLG<>'N' AND (INT_ORG_FLG<>'Y' OR PRTNR_FLG<>'N')) compute statistics ;
Performance Tuning :: Index Creation?
Aug 9, 2010is there any way to reduce the index creation time.
in my case one index creation took 5 minute and there are 5 indexes , so it took 25 minutes.
Performance Tuning :: Index With IN Statement
Jan 18, 2012I have the following problem. When I used in the IN-Statement fixed values e.q. 197321,197322,197323 ..., the index i_tab2_index works fine (index range scan).
But when I used in the IN-Statement an Sub-Select, the index i_tab2_index doesn't work (fast full scan)!My scale indices and used Selects:
CREATE INDEX i_tab1_index ON tab1 ( datum, flag_inst );
CREATE INDEX i_tab2_index ON tab2 ( tab2Idx, kontro );
SELECT count(epidx) as rowAnz
FROM tab2
WHERE tab2Idx IN ( SELECT tab1IDX FROM tab1
WHERE datum BETWEEN '20120117' AND '20120117'
AND flag_inst = '1' )
AND kontro = '9876521'
[code]...
Performance Tuning :: Index Monitoring
Aug 26, 2010get all the unused index in the system , if i put this query in batch job and execute it every night upto one months and store its data in a table and after one months i can get all the used indexes and left would be our unused indexes.
select
distinct p.object_name c1
from
dba_hist_sql_plan p,
dba_hist_sqlstat s
[Code]....
Performance Tuning :: Proper Index Is Not Used
Oct 17, 2012I have a table whose size is 2.3 GB and there are two indexes on it. One index is based on a Date column whose size is 900 MB, and the Other index consists of 5 columns including the date column, and the size is almost 2GB. But when i query the table using the Date column, it is doing a range scan on the second index which is almost the same size as the table. why is it not using the first index? What steps should i take so that it uses the First index without passing hints.
View 4 Replies View RelatedPerformance Tuning :: Difference Between Index Rebuild And Index Rebuild Online?
Jan 10, 2011What is the difference between index rebuild and index rebuild online.
View 3 Replies View RelatedPerformance Tuning :: How To Use Index On (ON In MERGE Statement)
Apr 6, 2011mbr has 60,000 rows and member has 60,000 rows approx. two tables have indexes on ssn, and citi_no on them.
PK of mbr : mbr_id
PK of member : mbr_id
other columns are not PK, and have no index on it.
I'm wondering why the statment doesn't use index while ssn and citi_no have index.
MERGE INTO mbr t
USING (SELECT mbr_id,citi_no
FROM member) a
ON (t.ssn = a.citi_no)
WHEN MATCHED THEN
UPDATE SET t.asis_mbr_id = a.mbr_id
where t.ssn not in(select ssn from mbr group by ssn having count(*) > 1)
Performance Tuning :: Index On Foreign Keys?
Jul 22, 2010I have to create indexes on foreign key columns ,now if composite index is already there with foreign key column then that will work or i will have to create a single column index.
View 17 Replies View RelatedPerformance Tuning :: Clustering Factor In Index?
Dec 15, 2010I am just curious to know what is clustering factor in index and How is it impartant in a sql tuning perspective ?
View 3 Replies View RelatedPerformance Tuning :: How To Find Index To Rebuilt
Oct 3, 2011i am trying to find the index want to rebuild or not for that i have analyzed that index after that i don't know how to calculate the ration could any one steps to do calculate the following ratio
Run the ANALYZE INDEX command on the index to validate its structure and then calculate the ratio of LF_BLK_LEN/LF_BLK_LEN+BR_BLK_LEN and if it isn?t near 1.0 (i.e. greater than 0.7 or so) then the index should be rebuilt. Or if the ratio BR_BLK_LEN/ LF_BLK_LEN+BR_BLK_LEN is nearing 0.3.
Performance Tuning :: Join Condition In Index?
Mar 14, 2012For a hash join statement, is it beneficial to have the join condition objects in the index as well as the objects in the where clause?
View 19 Replies View RelatedPerformance Tuning :: Force Subquery To Use Index?
Aug 5, 2010I have the following query:
Select
tag0.TAG_VALUE pid, tag1.TAG_VALUE, tag2.TAG_VALUE From TAGGER.TAGGABLE_RESOURCE r
, TAGGER.TAG tag0
, TAGGER.TAG tag1
, TAGGER.TAG tag2
where 1=1
[code]....
This runs in about 400ms. Now I replace this:
ANDtag0.TAG_TYPE in (4602, 5228)
ANDtag1.TAG_TYPE in (4612, 5225)
ANDtag2.TAG_TYPE in (4613, 5226)
with this:
ANDtag0.TAG_TYPE in (select COLUMN_VALUE from ( select * from table( TAGGER.GET_IDS_OF_SIMILAR_TAG_TYPES('Patient ID') ) x1 ))
ANDtag1.TAG_TYPE in (select COLUMN_VALUE from ( select * from table( TAGGER.GET_IDS_OF_SIMILAR_TAG_TYPES('Patients Sex') )x2 ))
ANDtag2.TAG_TYPE in (select COLUMN_VALUE from ( select * from table( TAGGER.GET_IDS_OF_SIMILAR_TAG_TYPES('Patients Birth Date') ) x3 ))
So instead of hard coding the IDs there is a function that looks them up. The function itself is reporting that it runs in 0ms. But when I run the new query:
Select
tag0.TAG_VALUE pid, tag1.TAG_VALUE, tag2.TAG_VALUE From TAGGER.TAGGABLE_RESOURCE r
, TAGGER.TAG tag0
, TAGGER.TAG tag1
, TAGGER.TAG tag2
where 1=1
[code]....
it takes around 6s to run. I have looked at the explain plans it it seems as though the function based approach is triggering a full table scan of 'TAG'.
I have tried it with query hints to use index, but it doesn't change the execution plan, or the query time.
The explain plan for the quick query is:
PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------
Plan hash value: 1031492929
---------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
[code]....
And the slow one is:
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------
Plan hash value: 2741657371
----------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |Te
----------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 20M| 1602M|
[code]....
Performance Tuning :: Why Oracle Doesn't Use The Index
Dec 2, 2010I have a table "NEWS_COMMENT" like this:
Name Type
------- --------------
ID NUMBER(8)
USERID NUMBER(8)
SORT_TEXT VARCHAR2(100)
TEXT VARCHAR2(1000)
DATE DATE
VALID VARCHAR2(1)
CODNEW NUMBER(10)
The table has a normal index for the userid column.
There is a query that looks for the differents CODNEW for a USERID but allways the CODNEW has to be greater than 2248833
select codnew from news-comment where userid=2914655 and valid='N' and codnew>2248833
I have created a new index for this kind of querys
create index coment_new_IDX on news_comment
(CASE WHEN codnew >2248833 and valid='N' THEN userid ELSE NULL END )
but oracle doesn't use it. I have used a hint to force it but doesn't run.