SQL & PL/SQL :: Performance Tuning In Large Inserts
Jan 19, 2011
I want to load 10 millions records from staging table to master table.One logic must be take during the load, the logic is rows already present in master table means, we need to update corresponding rows in master table otherwise rows insert in target table.
I have been using bulk collect and forall method to load data. it shows better performance compare then cursor row by row process. As per oracle doucmentation, we cannot use SELECT statements inside FORALL condition so we could not use logic inside the forall condition.
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Aug 7, 2012
There is a detail table
There is a summary table
During batch process record is entered in detail table as well as summary table.
The process first checks if record exists in summary table for same group_no and if 'yes' then "updates" the record with the newly added amount (sums it) else inserts a new record
Whereas in the detail table it inserts the record directly
detail table :
group_no doc_no amount
101 doc1 100
101 doc2 200
102 doc3 300
102 doc4 400
summary table :
group_no amount
101 300
102 700
Now if the batch process runs in parallel, (out of many) two different sessions insert same group_no; This is because while sesond session inserts a record, first session inserting the same record (group_no) has not yet committed ; So second session Not knowing that already there is same Group_no (101) inserted, again inserts another record with same group_no rather than summing it.
Can it be solved without using temp table, select for update?
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Aug 26, 2011
I am working with an online application with the database in Oracle 10G. We have a table with 10 million rows and this table is subjected to grow in future also. Moreover we cannot archive some of these rows as these records are required for referencing.
We have all necessary indexes on the table but querying this table takes a lot of time especially when it is joined with other tables. some methods with which I can manage this table in a better way so that queries joining this table would execute faster..
SELECT
TAB1.C6,
TAB1.C8,
TAB1.C10,
TAB3.C4,
[code]....
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Mar 28, 2011
I have several large tables in the live system! Those table are store historical information.
current situation:
Now, A table record was 129 million rows.
Every month added 4.5M records to this table.
This table data size 17GB and index size 28GB.
I have only 30 GB available free space on disk!
How to split this table to small pieces (partition table by month)?
What is the best approach?
I would like to do partitioning on this table month by month.
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Aug 15, 2011
I 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).
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Apr 5, 2012
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]....
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Jul 12, 2010
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?
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Oct 31, 2011
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].....
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Sep 30, 2010
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'.
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Jun 16, 2010
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?
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Oct 20, 2010
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 ?
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Jun 16, 2011
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?
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Nov 15, 2010
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?
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Apr 12, 2013
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.
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Aug 9, 2010
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.
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Dec 6, 2011
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?
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Oct 17, 2011
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]...
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Sep 3, 2010
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.
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Mar 17, 2012
are 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 ?
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Mar 27, 2013
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!
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Jul 4, 2012
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$lock l
WHERE type = 'TX'
AND ctime >= 2000
AND l.inst_id = se.inst_id
AND l.sid = se.sid)
AND sq.inst_id = se.inst_id);
[code]....
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Nov 2, 2012
I see one of my SQL's which is ran by the user on a 10.2.0.3 database changing its SQL_ID after some runs even if the query is not changed a bit! However the HASH VALUE for this query remains the same.
how a same query can have different SQL_ID's but same HASH_VALUE?
Note: Statistics are not modified on the base tables of this query.
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Aug 10, 2011
I am running Oracle 10.2.0.1.0 on MS Windows 2003 server 64-bit with 16G RAM.
Here is the findings for my Oracle database.
SQL> select * * from v$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?
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Jul 11, 2012
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 ?
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Mar 17, 2006
How can I disable redo generation for DML statements.
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Jul 26, 2011
I am getting enq: TS - contention as top event in AWR Report.where can i look into database to fix this issue.
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Aug 14, 2010
I want to run some OLTP benchmarks on my system. I have looked up the TPC-E benchmarking suite .. but the documentation on the site makes no sense to me .
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May 20, 2010
My DB is oracle10g.
I have AWR report comparison for two different days. I want to find the below things.
1. Which day has better performance?
2. What are the top two findings on the report.
I attached the report.
Here are my answer. Please correct me if i am wrong.
1. Which day has better performance? Second day has higher load. Since redosize is showing very high.
2. What are the top two findings on the report.
a) Compared to two days, first day, little bit more I/0 wait for single block read.
b) Compared to two days, 2nd day, it takes higher CPU.
However, which day is best compared to two days?
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Jul 12, 2013
I have installed database in one server. I would like to enable AWR into it. Statistics_level is set to Typical. While running the below script to enable the AWR, its gives error -
SQL> exec dbms_scheduler.enable('GATHER_STATS_JOBS');
BEGIN dbms_scheduler.enable('GATHER_STATS_JOBS'); END;
*
ERROR at line 1:
ORA-27476: "SYS.GATHER_STATS_JOBS" does not exist
ORA-06512: at "SYS.DBMS_ISCHED", line 4343
ORA-06512: at "SYS.DBMS_SCHEDULER", line 2802
ORA-06512: at line 1
make AWR automatical generation.
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Aug 31, 2010
In my awr reports I have CPU time(in seconds) as one of top 5 timed events.Does that mean oracle is waiting for my cpu to execute the statements.But my cpu usage is 0-10% always
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