So I was reading about indexes here:[URL]...1Is there any reason to NOT use an index? If there aren't, then should you use an index on every column on every table?
What is the general best practice with indexes? After reading the section, it seems that there are only positive impacts of using an index, so why are they not automatically created?
I have a base table with ~20 mio. records with two FAST REFRESH Materialized Views based on that table using various aggregate functions in their view definition.
The problem is, when e.g. one record changes in the base table, I see two records in the MV log table MLOG$, but invoking the fast refresh mechanism by using using:
dbms_snapshot.refresh('mv1', 'f');
dbms_snapshot.refresh('mv2', 'f');
Is still running after ~20 minutes now.
what analyzing a table does to existing indexes? Do I need to rebuild the indexes after dbms_stats.gather_table_stats command ?
View 4 Replies View RelatedBelow query is getting delayed becasue of BitMap Indexes on the table. I am trying to avoid indexes by using Hints in the query but unable to do so, Details are as follows.
explain plan for
SELECT cbu_cid, cbu_cid_customer_en_nm,
COUNT (billg_acct_no) AS billg_acct_no,
SUM (subscriber_cnt) AS subscriber_cnt
FROM daily_view
WHERE (billg_system_id = 'TM' AND mktg_sub_segment_a_nm = 'TM')
AND (cbu_cid NOT IN ('0001988048', '0001379962', '0001350469'))
GROUP BY cbu_cid, cbu_cid_customer_en_nm
HAVING SUM (subscriber_cnt) > 10
ORDER BY subscriber_cnt DESC;
[code]....
I have tried with ALL_ROWS & PARALLEL.how to avoid above two indexes in a query.
So our situation is pretty simple. We have 3 tables.
A, B and C
the model is A->>B->>C
Currently A, B and C are range partitioned on a key created_date however it's typical that only C is every qualfied with created date. There is a foreign key from B -> A and C -> Bhave many queries where the data is identified by state that is indexed currently non partitioned on columns in A ... there are also indexes on the foreign keys that get from C -> B -> A. Again these are non partitioned indexes at this time.
It is typical that we qualifier A on either account or user or both. There are indexes (non partitioned on these) We have a problem with now because many of the queries use leading wildcards ie. account like '%ACCOUNT' etc. This often results in large full table scans. Our solution has been to remove the leading wildcard.
We are wondering how we can benefit from partitioning and or sub partitioning table A. since it's partitioned on created_date but rarely qualified by that. We are also wondering where and how we can benefit from either global partitioned index or local partitioned indexes on tables A. We suspect that the index on the foreign key from C to B could be a local partitioned index.
getting all indexes script in particular schema.
View 4 Replies View RelatedI have tried a lot by alternate solutions like rearranging the order of tables in join and moving where conditions before but no success...Its a bottleneck and I could not have indexes on these tables in production...I want to change the approach in subquery
SELECT
g.COLUMN1,
g.COLUMN2,
e.COLUMN3,
g.COLUMN4,
MIN(e.dat1) KEEP ( DENSE_RANK FIRST ORDER BY date2 Desc) * -1,
min(to_char(date3,'dd-mm-yyyy'))
[code]....
I don't have any dba privileges, can you share a scripts which can tell how many block my query is fetching with or without indexes. How do i also get buffer hit, how can i get i/o without sql trace as i don't have access to dump_dest
I have a below query
SELECT DISTINCT ser_id AS STA_ser_id, rct_name AS STA_name
FROM sd_servicecalls, rep_codes, rep_codes_text
WHERE ser_sta_oid = rcd_oid
AND rcd_oid = rct_rcd_oid
AND rct_name IN ('New', 'Awaiting Approval', 'Approved', 'In Progress', 'Awaiting Supplier', 'Awaiting RFC', 'Awaiting Release', 'Pending Release', 'On Hold', 'Resolved', 'Implemented', 'Closed');
Does large hash value in explain plan mean more resource needed and more time to execute the query, How can i use ADDM for the above sql.
getting how many local and global indexes on particular oracle table
View 2 Replies View RelatedI am having Oracle 9i relaese 2 on my db server. I am getting the following error every time I try to create a bitmap index:-
ORA-00439: feature not enabled: Bit-mapped indexes
I have queried the v$option table .Here the value of parameter Bit-mapped indexes is FALSE.
The result of v$version is :-
Oracle9i Release 9.2.0.1.0 - 64bit Production
PL/SQL Release 9.2.0.1.0 - Production
CORE 9.2.0.1.0 Production
TNS for Solaris: Version 9.2.0.1.0 - Production
NLSRTL Version 9.2.0.1.0 - Production
Actually when we created the database our installation was halted . so we manually created the database using Create database command.
How can we enable the BITMAP Index Feature now.
I Want to tune the attached query. I have tried by creating the normal indexes and composite indexes on the fields . I feel that , Only normal index is required for this instead of composite index?
11:15:19 SQL> @slot.sql
11:16:03 SQL>
11:16:03 SQL> drop table slot purge;
Table dropped.
Elapsed: 00:00:00.05
11:16:03 SQL>
11:16:03 SQL> create table slot
11:16:03 2 (
11:16:03 3 id varchar2 (40) not null,
[code]....
- dynamic sampling used for this statement
22 rows selected.
16:28:32 SQL> create bitmap index bp_idx_ag_id on transactions(type);
create bitmap index bp_idx_ag_id on transactions(type)
*
ERROR at line 1:ORA-25122: Only LOCAL bitmap indexes are permitted on partitioned tables
how to create bitmap index on partitiioned tables
Create small functional indexes for special cases in very large tables.
When there is a column having one values in 99% records and another values that have to be search for, it is possible to create an index using null value. Index will be small and the rebuild fast.
Example
create index vh_tst_decode_ind_if1 on vh_tst_decode_ind
(decode(S,'I','I',null),style)
It is possible to do index more selective when the key is updated and there are many records to create more levels in b-tree.
create index vh_tst_decode_ind_if3 on vh_tst_decode_ind
(decode(S,'I','I',null),
decode(S,'I',style,null)
)
To access the record can by like:
SQL> select --+ index(vh_tst_decode_ind_if3)
2 style ,count(*)
3 from vh_tst_decode_ind
4 where
5 decode(S,'I','I',null)='I'
6 group by style
7 ;
[code]....
Lot of my tables are just for join purpose , a table with just with two columns both FK , I did not add any composite PK to this table, lot my queries uses this table , because it does not have composite PK will the query be slow ? what I have to do to increase performance querying with such tables ?
View 5 Replies View RelatedLooking 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?
I 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].....
How 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'.
I 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?
There 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 ?
How 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?
Testing 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?
I 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.
Somewhere 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.
I 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?
The 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]...
what the principal things to look at when we have for the same query different performance results are?I have 2 different bases: the plan and data are the same but performance results are very differents.
View 10 Replies View Relatedare the most important performance keys we have to calculate or take in account to preserve or to increase the DB performance in terms of response times, and whatsoever according to performance ?
View 8 Replies View RelatedRDBMS - 11.1.0.7, I it possible to convert indexes of a non-partitioned table to hash partitioned indexes by retaining table as non-partitioned?
If yes, is this what it is Creating a Hash-Partitioned Global Index - can be created for partitioned and non-partitioned tables?
I am working on an assignement where client is using Oracle 10g but stuck to using RBO Now the application team, from the GUI available to them build dynamic queries and some of them run very slow.
Neither the code can not be changed to tune the queries nor do we get the exact step in the plan which is an issue (being RBO).For some long running queries the Tuning advisor is not producing any recommendations.
Another hurdle is that all the application users are using same application user id so we can not write a logon trigger to use CBO for some particular queries to see what is happening in the background!
I want to tuning the next sql sentence. In this sql I want to get the hash_value and sql_text of the sentences that it's causing TX blocks. Is it possible?. This sentence works fine but sometimes It's slow.
SELECT DISTINCT hash_value,
sql_text
FROM gv$sql sq
WHERE hash_value IN (SELECT DISTINCT prev_hash_value
FROM gv$session se
WHERE sid IN (SELECT sid
FROM gv$lock l
WHERE type = 'TX'
AND ctime >= 2000
AND l.inst_id = se.inst_id
AND l.sid = se.sid)
AND sq.inst_id = se.inst_id);
[code]....