how joins work with in-line views.I have a query and its explain plan as below:
SELECT e.ename,e.deptno,d.dname FROM
dept d,
emp e
WHERE e.deptno=d.deptno
AND e.deptno=20
[code]....
I do not find any difference in both the explain plans. Both are same. In my second query, the filtered rows will be joined to dept table. And hence the baggage will reduce.But how can I verify that in-line view has worked better?
When to use inline query and to use join.
View 3 Replies View RelatedI want to know how the Oracle optimizer choose joins and apply them while executing the query. So that I will insure about optimizer join before writing any query.
View 2 Replies View RelatedWe are using the below query to create a Materialized View but it has been running since 3 hours. It is an Oracle 9i database running in HP-UX.The quey is as follows,
(SELECT
/*+ use_nl(A) parallel (A,4)*/
A.ICD_CODE AS ICD_CODE,
A.ICD_DESC AS ICD_DESC,
A.PROC_GROUP as PROC_GROUP,
B.COMPL_ICD_CODE AS COMPL_ICD_CODE,
B.COMPL_GRP_TXT AS COMPL_GRP_TXT,
C.PROC_TYPE AS PROC_TYPE ,
[code]....
SQL> select * from v$version;
BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi
PL/SQL Release 10.2.0.4.0 - Production
CORE 10.2.0.4.0 Production
TNS for Solaris: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production
5 rows selected.
I have a problem with views and nested selects which I cannot explain. Here is a trimed down version of the research I have done. notice the following:
1) all code is executed from the same user CDRNORMALCODE. this user has all views and procedural code
2) all data is owned by a different user CDRDATA. This user has no views and no code.
My problem is this:
If I reference the table directly with a delete statement that uses a nested select (i.e. IN clause with select), the index I expect and want is used.But if I execute the same delete but reference even the most simple of views (select * from <table>) instead of the table itself, then a full table scan is done of the table.
Here is an execute against the table directly (owned by cdrdata). Notice the reference to the table in the table schema on line 3. Also please notice INDEX RANGE SCAN BSNSS_CLSS_CASE_RULE_FK1 at the bottom of the plan.
SQL> show user
USER is "CDRNORMALCODE"
SQL>
SQL> explain plan for
2 delete
[code]...
OK, here is an update. The views I am useing normally have instead of triggers on them. If I remove the instead of trigger the problem looks like it goes away, when I put the trigger back the problem comes back.But why would an instead-of-trigger change the query plan for a view?
SQL> DELETE FROM PLAN_TABLE;
5 rows deleted.
SQL> explain plan for
2 delete
3 from BSNSS_CLSS_MNR_CASE_RULE_SV
[code]...
is there some open source or free tool which can graphical display V$ Views. Can TOAD do that in a good maner?
in UNIX there is the "sar" command, but a Java tool "ksar" for displaying the statistics in user friendly fashion.
I am working on Oracle 10g and Below is my query which is taking 30min. to execute. I am using two inline view and then make joins on these inline view because of i think it Degrade Performance.
Query :-
SELECT LEVEL_USER,
TRIAL_NO,
UNIT_NO,
COUNTRY_CODE,
PERSONNEL_NO,
[code].......
Note :- i have Attached the explain Plan for the same .Please let me know how can i improve performance of this Query.
I have a query I am trying to tune. It presently takes anywhere from 15 minutes to two hours to run, depending on how many records the client has. But it needs to run several hundred times, and finish over the course of a weekend. When it runs over, we have problems.
Here's the basic structure of the query:
CODESELECT ...
FROM main_tab,
tab_a,
tab_b,
tab_c,
...
tab_z
WHERE main_tab.client_id = :1
AND main_tab.unique_id = tab_a.unique_id(+)
AND main_tab.unique_id = tab_b.unique_id(+)
AND main_tab.unique_id = tab_c.unique_id(+)
...
AND main_tab.unique_id = tab_z.unique_id(+);
All of the tables are indexed (and statistics are gathered) on the field unique_idMain_tab has an index on client_id.There is a one-to-one join (sometimes one-to-zero, thus the outer join) from the main_tab table to all the other tables.These are static tables, they're wiped and recreated - no changes, inserts, deletes.
By default, the optimizer does a full table scan and then a hash join on every single of the 26 tab_a through tab_z tables, only using the index on main_tab.
By the way I can add indexes, possibly even to the point of adding an index on some tables that would include all the fields found in the select clause on that table. But I cannot change the table structure (by, say, combining these tables together).
Looking 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 RelatedI have a created a materialized view which is based on a view on remote database. Now how do I refresh the view.
Materialized view is created by
CREATE MATERIALIZED VIEW mv_employee_name
AS SELECT EMPLID, EMPL_NAME
FROM VEMPDATA@REMOTEDB
WHERE REGION = 'US';
I am wondering how the refersh happens or how do I specify the refresh clause.REFRESH FAST option is looking for VIEW LOG on the master table but in this case its a remote view, so I cannot create any object on remote db.
I am removing sal column from table tab_emp; i want to check whether any materialized view or view using this column by querying using data dictionary :- if i use like condition against query column of all_mviews it is throwing error sicne it is long data type. is there a way to search it without creating any function and use it in a query.
View 3 Replies View RelatedI have to convert some existing materialized views (fast refresh) to partition materialized views.
Database version is oracle 10.1.0.4. I have decided to use on prebuilt table option to do the partitioning as it minimizes the time to transfer from the master site.
1) stop replication
1) create interim tables with similar structure as the materialized views
2) transfer all data from the materialized views to the interim tables
4) script out the materialized views structure and add in on prebuilt table option in the scripts
5) drop the materialized views
6) rename the interim tables with the same name as the materialized views
7) run the scripts to create the materialized views with on prebuilt table option
8) refresh the newly created materialized views -> it should take a short time since I am using on prebuilt table option
But I am facing one major issue. That is if I drop the materialized views, the materialized view logs of the master tables are purged. When the materialized views are refreshed fast, there are some data missing. the data that are purged out when the materialized view are dropped.
Do you happen to know other ways that existing materialized views can be converted to partitioned materialized views? Do you have any workaround to prevent the materialized view logs from being purged?
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$lock l
WHERE type = 'TX'
AND ctime >= 2000
AND l.inst_id = se.inst_id
AND l.sid = se.sid)
AND sq.inst_id = se.inst_id);
[code]....
I see one of my SQL's which is ran by the user on a 10.2.0.3 database changing its SQL_ID after some runs even if the query is not changed a bit! However the HASH VALUE for this query remains the same.
how a same query can have different SQL_ID's but same HASH_VALUE?
Note: Statistics are not modified on the base tables of this query.
I am running Oracle 10.2.0.1.0 on MS Windows 2003 server 64-bit with 16G RAM.
Here is the findings for my Oracle database.
SQL> select * * from v$sgainfo;
NAME BYTES RES
-------------------------------- ---------- ---
Fixed SGA Size 1293560 No
Redo Buffers 7094272 No
Buffer Cache Size 830472192 Yes
[code]...
I find that the SGA component "Buffer Cache" is decreasing from the start "1.8G" and down to now 0.8G. On the other hand, the component "Shared Pool" is increasing from the start 0.3G to now 1.2G. I noticed that there are 100 operations of shrinking of "Buffer cache" and growth of "Shared Pool" in Oracle every day.Is it a indicator that I should raise up the SGA_MAX_SIZE?
I tried to increase the SGA_MAX_SIZE to 4G. But I cannot start the Oracle afterward.Is it a limitation of MS Windows(OS) or Oracle?I set the SGA_MAX_SIZE to 3G. This time, I can startup Oracle.What is the optimum/maximum I can set to SGA_MAX_SIZE?Is there any adverse effect/concern when setting the SGA_MAX_SIZE more than 2G?
Here i have three tier application. I want to know it host name from sid or sqlid . I want to know which query run on which host. Because i have one user from application to database. So i want to know which query consume more time on which host ?
View 19 Replies View RelatedHow can I disable redo generation for DML statements.
View 25 Replies View Related