TX - Index Contention On Update
Sep 3, 2012
I have a UPDATE statement which sets values on non-indexes columns and do not use indexed-column in where clause (so every column used in statement are not indexes). Lastly, I had some problem with database and saw in ASH report in TOP SQLs that update with events enq: TX - index contention and buffer busy waits. What does it mean? I read a lot of information about index contention, but always related to INSERT and DELETE. What has UPDATE to do with this contention?
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Aug 27, 2012
We have occurrences of enq : TX - index contentions in the database. Using the SQL ID, we have identified the INSERT statement and the table which they are trying to insert.
This table has almost 25 different indexes, some of which are unique as well.I am wondering how to identify the actual index causing issue, out of these 25 indexes.
Is there any way to pin point to the name of index which is causing the lock?My plan is, once the index is identified, I would like to check the extents and inittrans and other attributes of this index to fix.
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Jun 23, 2011
I've got a table which has no unique identifier for a row. I have a field for an ID value but somhow there are duplicate values in this field.
Now I want to create an unique index over this field but therefore I have to remove the duplicate values.
So what I need is an update statement, maybe in a for each loop, which updates the ID field in each row starting with 1 and increasing the value.
In Informix there is a rowid value which is automatically set by Informix. But I think there´s no correspondent function/value in Oracle....
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Nov 26, 2012
I am having trouble figuring out why an update statment is ignoring the primary kiy index when performing an update through the application. The index IS used when the update is run from sql*plus or other sql tools.
The statement is very simple:
update ITEM_MASTER set COST = :1 where SMARTPART_NUM = :2;
ITEM_MASTER has unique, primary key index on SMARTPART_NUM
When I use OEM and other tools, I can see the index is not used in the exlain plan, and the query has a high CPU cost due to the full table scan. The table is analyzed, lately using 100%. Table rowcount is 229768
SELECT column_name, num_distinct, num_buckets, histogram, trunc(last_analyzed) ANALYZED FROM USER_TAB_COL_STATISTICS
WHERE table_name = 'ITEM_MASTER' AND column_name = 'SMARTPART_NUM';
COLUMN_NAME NUM_DISTINCT NUM_BUCKETS HISTOGRAM ANALYZED
------------------------------ ------------ ----------- --------------- ---------
SMARTPART_NUM 198417 254 HEIGHT BALANCED 25-NOV-12
The database is Oracle Database 10g Release 10.2.0.4.0 - 64bit Production (on Windows, standard edition)
Here are parameters related to optimizer:
optimizer_dynamic_sampling integer 2
optimizer_features_enable string 10.2.0.4
optimizer_index_caching integer 0
optimizer_index_cost_adj integer 100
optimizer_mode string ALL_ROWS
optimizer_secure_view_merging boolean TRUE
We've tried rebuilding the indexes then re-analyzing, dropping stats and locking at zero, using various sample sizes; none have any impact.
We wondered if the bind variables are causing this, though in testing outside the application, we tried pl/sql and sql batches to mimic the passing of values into the binds, and all still used the index.
Other than putting a hint into SQL in the application (we'd have to ask for a customization), how can I "fix" the database to use the index? In other words, how can I make the database see that the cost of a FTS is much higher than using the index, whenever it sees these updates (either from sql or the application)? This is the simplest example, but we have 4-5 SQL updates on this and other tables that are ignoring the indexes and using full table scans, so we'd like to fix it for all.
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Oct 10, 2012
In my current project, I am handling an Oracle database with version 10.2.0.3. I analyzed the AWR report for the past month abd saw the following wait events consistently:
CPU time - 45.6% (% Total Call Time)
db file sequential read - 30.6% (% Total Call Time)
enq: TX - row lock contention - 18.8 % (% Total Call Time)
I have uploaded the report for your reference.What should be my approach to troubleshoot this?
Attached File(s)
awr_report.html ( 382.28K )
Number of downloads: 6
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Aug 30, 2011
In the program i wrote, posted in this thread I parallelize 340 jobs.
To do this, according to oracle documentation, i set the job_queue_processes parameters to 450. This works fine, all jobs are submitted, but, when i chek the dba_scheduler_job_run_details, i notice that there is a difference between REQ_START_DATE, which is my requested start date, when i enabled my job, and the ACTUAL_START_DATE, which is the date on which Oracle start this process.
And the more i submit job, the more difference between ACTUAL_START_DATE and REQ_START_DATE increase. But for each job, run duration is less than 1second. I check the processes parameter, and it is set to 100. if i have to increase the processes parameter to 450 too ?
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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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Oct 22, 2010
We are suffering from very bad application response for last few days, when i try to check and drill down, where the actual contention is? I came to know that there may be contention on data blocks, which may be a prime reason for degraded performance. Herewith i'm pasting my actual stats of gathered from v$waitstat. I gone through some of asktom docs and find that there may be a problem with freelist or segment space management. My data tablespace is segment space management = Manual.
My main question is
1) Should i need to increase freelist value (Right now my value is 1)
2) Or i have to move on segment space management = auto
SQL> select * from v$waitstat;
CLASS COUNT TIME
------------------ ---------- ----------
data block 2022 4052
sort block 0 0
save undo block 0 0
segment header 1 1
save undo header 0 0
free list 0 0
extent map 0 0
1st level bmb 0 0
2nd level bmb 0 0
3rd level bmb 0 0
bitmap block 0 0
bitmap index block 0 0
file header block 0 0
unused 0 0
system undo header 0 0
system undo block 0 0
undo header 6 0
undo block 0 0
18 rows selected.
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Nov 19, 2012
I am having enq: TX - row lock contention in top wait event. it is occurring between 10pm - 2am.
We are having sqlloader job running every one hour(conventional path). But for the specific period of time i am getting "Global Enqueue Services Deadlock detected". Between 10-5. I analyzed related trace file it is make me little confusion.I found there are four insert query culprit for this locking. out of four sql , tow of them are ran by same SID, other two insert ran by same id. I got confused because how same sid locking them self. trace file below. during this period oracle maintenance window is active.
Trace file:
*** 2012-10-09 03:40:31.135
user session for deadlock lock 0x15365e060
sid: 1104 ser: 22256 audsid: 8797820 user: 49/iurth flags: 0x45
pid: 71 O/S info: user: oracle, term: UNKNOWN, ospid: 8601
image: oracle@sgh0909
client details:
[code]....
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Oct 19, 2010
I have created a table: INDEX_SIZE_TRACKING with the following attributes
Index Name: name of the index. Type: VARCHAR(255). This is the primary key of the table.
Allocated Space: the memory space (in bytes) allocated to the index. Type: NUMBER
Used Space: the memory space used by the index. Type: NUMBER
Last Update: the time when index details are updated to this table. Type: VARCHAR(255)
I want to write a PL/SQL script to query index statistics data and update tracking entries in the INDEX_SIZE_TRACKING table. If there is no existing entry for the index, create a new one; otherwise, update the existing one. have a PL/SQL statement that can do this in oracle XE?
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Jun 27, 2012
I am on 11.2.0.3 Enterprise Edition. We are using the new feature "Composite Domain Index" for a Domain index on a very large table (>250.000.000 rows). It really works with mixed queries. We added two number columns using FILTER BY.We have lots of DML on this table. Therefore, we are executing synchronize and optimize once the week. The synch behaves pretty normal. But "optimize_index" takes a very very long time to complete. I have switsched on 'logging' for the optimize process. The $I table takes some time but is finished normally. But the optimization of the $S table (that is the table created for the CDI feature) is running over 12 hours now - and far from being finished. From the logfile, I can see that it optimizes 1000 rows every 20 minutes. Here is the output of the logfile:
Oracle Text, 11.2.0.3.0
14:33:05 06/26/12 begin logging
14:33:05 06/26/12 event
14:33:05 06/26/12 process $N for optimize: SEQDEV.GEN_GES_DESCRIPTION_CTX_I
14:33:16 06/26/12
14:33:16 06/26/12
[code]....
I haven't found a recommendation from Oracle not to use "optimize_index" for Domain Indexes with CDI. But in my case, it would be much faster just to drop and recreate the Domain Index in question.
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Jun 28, 2011
I 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.
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Jun 23, 2011
I have a global index and I want to convert it to local index.Is there a way to recreate local index with out dropping the global index.
I can create a local index first and then drop the global index. But is there a way to create it with out dropping the global index, just convert it.
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Nov 29, 2010
I am facing the error "ORA-01502: index or partition of such index is in unusable state " while loading the text data using
sql loader with direct path (direct = Y ,rows = 10000) option. Table consists an composite non unique index. If I query the dba indexes for the effected index it shows the index status as VALID. There was no maintaince done on the effected table or index. I have tried loading the same data using conventional path but didn't found any issues for the same.
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Nov 19, 2010
I 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?
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Aug 9, 2013
How to force an index if the table not using the index?
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Jul 11, 2012
Can we create non-cluster index on a clustered index?
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Aug 3, 2010
Any on give explanation for difference between Index and Clustered Index?
It will be great if i get explanation how memory allocation and Execution takes place.?
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Jan 10, 2011
What is the difference between index rebuild and index rebuild online.
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May 14, 2010
I have a base table (Table A) block with multiple records displayed. I need to track audits to this underlying table in the following way:
If user updates a field in the block I want the pre-changed record's audit fields to be set and I need to create a copy of the record with the changed values. Basically any changes will result in the record being logically deleted, and a copy record created with the newly changed values.
Tried to implement in the block's pre-update trigger which will call a package to directly update Table A then Insert into Table A, then requery the block. Is there a clean and efficient way to do this?
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Sep 7, 2010
I have to update 20 and 60 million records of a table. The update statement are
1> 20 million recs
update mycustomer set update_time=add_months(sysdate,240) where seq_num = 1;
commit;
2> 60 million recs
update mycustomer set update_time=sysdate-seq_num where seq_num <> 1;
commit;
Q1> Is there any way to improve performance
Q2> Will parallel dml improve performance
Q2> Would a pl/sql cursor make any difference in speed.
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Aug 17, 2010
This is my query:
UPDATE t_tt_hours a
SET a.sak_request = (
SELECT b.sak_request
FROM t_requests b, co c
[Code]...
The problem I am having is that it is updating all rows even when it is pulling back a null value for b.sak_request. I've tried adding b.sak_request is not null to the select statement like this:
UPDATE t_tt_hours a
SET a.sak_request = (
SELECT b.sak_request
FROM t_requests b, co c
WHERE b.nam_eds_tracking_id = c.id_dir_track_eds
[Code]...
but it doesn't seem to make a difference. The reason I need to do this is that the difference between where it matches with a valid (non-null) value is 396 rows vs. 12,484 rows which is too time consuming to run on my page.
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May 29, 2012
i want to create a trigger that will update a table when there is an insert or update.i can't across this error that i don't even know what it means "table %s.%s is mutating, trigger/function may not see it".
*Cause: A trigger (or a user defined plsql function that is referenced in this statement) attempted to look at (or modify) a table that was in the middle of being modified by the statement which fired it.
*Action: Rewrite the trigger (or function) so it does not read that table.
CREATE OR REPLACE TRIGGER set_date_end
BEFORE INSERT OR UPDATE OF issued ON shares_amount
FOR EACH ROW
DECLARE
BEGIN
INSERT INTO shares_amount(date_end) VALUES(SYSDATE);
END set_date_end;
/
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Mar 6, 2013
create table test1
( ID NUMBER(11)
,MEMBER_NMBR NUMBER(10)
,CODE_NMBR NUMBER(7)
,ROW_EFCTV_DT DATE
,ROW_TRMNTN_DT DATE
[code]....
insert into test1 values (11007,7462,32,'30/sep/2012','31/dec/9999',3,'25/sep/1998','AUTUMN',1,0,344);
insert into test1 values (11007,7462,32,'30/oct/2012','31/dec/9999',3,'25/sep/1998','AUTUMN',1,0,344);
IDMEMBER_NMBRCODE_NMBRROW_EFCTV_DTROW_TRMNTN_DTFLAG_NMBRBRTH_DTNAMECLAIM_CDAMT1AMT2
1100774623209/30/2012 00:0012/31/9999 00:00309/25/1998 00:00AUTUMN10344
1100774623210/30/2012 00:0012/31/9999 00:00309/25/1998 00:00AUTUMN10344
I have to update the row_trmntn_dt of first row to row_efctv_dt of 2nd row which is 30th Oct 2012 - 1 day i.e. 29th Oct 2012
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May 30, 2013
i am reading the columns value from different table but i want to update it with single update statement. such as how to update multiple columns (50 columns) of table with single update statement .. is there any sql statement available i know it how to do with pl/sql.
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Mar 21, 2011
I have one doubt about update command in sql. How to update the multiple rows with different values using update statment.
Eg:-
SQL> set linesize 500;
SQL> set pagesize 500;
SQL> select * from emp;
SQL> select empno,ename,sal from emp;
SQL> select empno,ename,sal from emp;
EMPNO ENAME SAL
---------- ---------- ----------
7839 KING 5000
7698 BLAKE 2850
7782 CLARK 2450
7566 JONES 2975
7654 MARTIN 1250
[Code]....
The above table contains 14 records. Now i would like to update the salary column with different values like
EMPNO SAL
===========
7839 18000
7698 20000
7782 5000
...
...
...
7934 25000
How to update above values with single update query.
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Jan 25, 2012
After many tests I can't make work and update of the same table inside the same table.
Trying to avoid Mutating Table Error now I have
ORA-00036: maximum number of recursive SQL levels (50) exceeded
Sample Data :
create table test_compound (USERID VARCHAR2(10),APP VARCHAR2(15),LAST_UPDATED_ON TIMESTAMP);
insert into test_compound values ('user1','1',systimestamp);
insert into test_compound values ('user2','2',systimestamp-4);
insert into test_compound values ('user3','3',systimestamp-6);
CREATE OR REPLACE TRIGGER trigger_test
FOR UPDATE ON test_compound
COMPOUND TRIGGER
TYPE t_tab IS TABLE OF VARCHAR2(50);
l_tab t_tab := t_tab();
[code].......
When I execute :
update test_compound
set last_updated_on=systimestamp
where userid='user1' and app='1';
The trigger should update the first row and all the data from test_compound table where userid='user1'. Maybe the problem is that updating the same table inside the trigger is firing in a recursive way the trigger.
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Jul 19, 2011
I have a column "empno" in EMP table and "deptno" in DEPT table . I want to update both the columns with single UPDATE statement. With out a creation of stored procedure or view(updating it through view).
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Oct 5, 2013
Let's consider such table that all rows fit into single block:
SQL> create table test as select rownum id, '$'||rownum name from dual connect by level <= 530;
Table created.
SQL> create index i_test on test(id);
Index created.
SQL>
SQL> begin
[code].....
why does approach with full scan take longer even if table occupies only one data block? PS. 11gR2
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Jul 21, 2011
I have table test1(id,name) and table test2(id,,name)
Now when I update name column of a row on test1 I want the same value to be updated for the same id in test2.
So I wrote this trigger but its not working
create trigger test_trigger after update on test1 for each row
begin
update test2 set name=new.name where test2.id=id
end
/
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