Server Administration :: Sessions And LGWR Locking?
Jul 13, 2010
We had an issue last week were we had a session with a very basic SQL query lock up the database, spiking the CPU at 100%. When you would kill the session, the lock would just jump to another session and so on. We finally had to restart the database since our clients were being kicked out. After the restart of the database, the LGWR ended up locking and held the CPU between 85-95%. The archive logs were switching every 5 minutes, when normally it would be every 45min. We spoke with Oracle Support, but they just ended up brushing the issue off and saying it was a hardware issue and were not able to provide any kind of backing to that.
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Apr 27, 2012
how to avoid oracle deadlock with two sessions. Here is my example, We use Select query with For Update in order to get the unique number from a table. When one user has accessed this query, while the other user tries, System gives a Performace slow and when checked it is due to locking of this select query with For update.
We don't want to use For update WAIT or FOR UPDATE NOWAIT since these will result in missing of number.
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Mar 9, 2012
My application is opening a lot of sessions in my DB server. I applied resource_limit=true and idle_time=15 min. ans assign this profile to all application user.
Now I am seeing a lot of sessions having status sniped in v$session.
I want to clean up these sniped sessions and what they mean.
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Aug 19, 2010
I am using oracle 10g as server in my lab. I faced some problems initially, but later after increasing the USERS tablespace it is working fine.
But there is still one problem. During the query execution some queries will be blocked and it doesn't leave any consequent queries to execute from the same user.
The blocked sessions will be displayed in the admin page under blocking sessions link. There is a option to kill the session. But when i do that, it affects all the users and the connection will be lost to all the users. again I have startup the database from beginning.
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Mar 26, 2013
I have a simple question about database sessions. The value of parameter "sessions" is set to 500 and the users connect to database through an application server(Jboss). There are more than 500 users connect to the database through application.
My question is, how more than 500 users can connect to the database without any issue, if we set the value of "sessions" parameter to 500?
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Feb 5, 2011
I have a table with counter value which will be incremented or decremented by several application servers.
SQL> select * from test;
COUNTER
----------
10
Application servers(multiple servers) will be running update against this row for increasing the counter value or decreasing the counter value.
update test set counter=counter+1;
update test set counter=counter-1;
update test set counter=counter+1;
update test set counter=counter+1;
So when update happens concurrently to this table will the counter value gets messed up?
I did a small test by opening multiple sessions for running update and the result I got for above update statement was 11,10,11,12.
But our developer is bit skeptical about this approach and he is using select for update and then updating the row.
Which approach will be better?
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Mar 30, 2011
I'm sure you are all familiar with proxy users, they've been around since 9i: orcl> create user low identified by low;
User created.
orcl> create user high identified by high;
User created.
orcl> grant dba to high;
Grant succeeded.
orcl> alter user high grant connect through low;
User altered.
orcl> connect low[high]/low
Connected.
orcl> sho user
USER is "HIGH"
orcl>
Is there any way that I can find out which of the current sessions was proxied, and through what user? I know that from within the session I can query my userenv context and find out, but I can't see how to do it otherwise. It must be possible: the audit trail records both the real user and the proxy user.
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Oct 27, 2010
I killed some 70 sessions which where inactive couple of days ago using alter system kill session(sid,serial#) immediate;
But even after killing them it still exists in the v$session view when I query select sid,serial# from v$session where username is not null; It has the same sid and serial#....I tried killing them every now and then but it still shows those exists
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May 25, 2010
We have quite a number of sessions in database MES (production) coming from another machine.
From v$session, the program is oracle@WID27 (TNS V1-V3). This WID27 (hostname) consists of quite a number of development databases inside. We have to trace which jobs are actually triggering this, as WID27 are not suppose to connect to production databases.
How can we tell whether the sessions came in is from dblink or from the machine itself?
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Nov 11, 2011
I have had the following problem open with Oracle support since March 2011 (8 months), and still no resolution.
When I export all our schema's on Sunday night it takes about 1 hour 50 minutes. When I export the same schema's on any other night it takes 7 hours. The only difference is that on Sunday at 4:00am we drop all connections in the connection pools and reestablish new connections. Then 19hours later on Sunday at 23:00 we perform the exports which only take 2 hours to complete.
I have also tried recreating the connections in the connection pools during the week, and the exports have then only taken 2 hours to complete. But the following night after the connections have been used during the day, the exports again take 7 hours. So it appears the export speed gets significantly slower when there are many open connections that have been used and not closed.
From the stats pack report I found 2 SQL statements internal to the export command, that had an order of magnitude in difference when looking at the elapsed execution time between the fast export, and the slow export (see below).
How to speed up the exports without having to drop and recreate the database connections in the connection pools each night.
FAST:
elapsed_time: 430.90
executions: 161,388
Module: exp@Oracle1 (TNS V1-V3)
SELECT COLNAME, COLNO, PROPERTY, NOLOG FROM SYS.EXU10CCL
WHERE CNO = :1 ORDER BY COLNO
elapsed_time: 264.29
executions: 50,349
Module: exp@Oracle1 (TNS V1-V3)
SELECT TOWNER, TNAME, NAME, LENGTH, PRECISION, SCALE, TYPE, ISNULL, CONNAME, COLID, INTCOLID, SEGCOLID, COMMENT$, DEFAULT$, DFLTLEN, ENABLED, DEFER, FLAGS, COLPROP, ADTNAME, ADTOWNER, CHARSETID, CHARSETFORM, FSPRECISION, LFPRECISION, CHARLEN, TFLAGS, 100 FROM SYS.EXU8COL
WHERE TOBJID = :1 ORDER BY INTCOLID
SLOW:
elapse_time: 8264.16
executions: 124,662
Module: exp@Oracle1 (TNS V1-V3)
SELECT COLNAME, COLNO, PROPERTY, NOLOG FROM SYS.EXU10CCL
WHERE CNO = :1 ORDER BY COLNO
elapsed_time: 3877.78
executions: 38,813
Module: exp@Oracle1 (TNS V1-V3)
SELECT TOWNER, TNAME, NAME, LENGTH, PRECISION, SCALE, TYPE, ISNULL, CONNAME, COLID, INTCOLID, SEGCOLID, COMMENT$, DEFAULT$, DFLTLEN, ENABLED, DEFER, FLAGS, COLPROP, ADTNAME, ADTOWNER, CHARSETID, CHARSETFORM, FSPRECISION, LFPRECISION, CHARLEN, TFLAGS, 100 FROM SYS.EXU8COL
WHERE TOBJID = :1 ORDER BY INTCOLID
I use the following export command for each schema:
$ORACLE_HOME/bin/exp user/pass file=somefile.dmp owner=$SCHEMA log=somelog.log buffer=9000000
I have an Oracle Standard edition 11.1.0.7 database on 64bit Linux with a 7GB SGA. I currently export (I use exp not datapump because datapump is a lot slower and we can't use parallel processing features of datapump on a standard edition database) approx 200 schema's each night. The export normally takes 1 hour 50 minutes which is approximately 2 schema's exported every minute. When the exports run slowly each export takes almost 2 minutes to complete.
The database has about 20 GB data and 50 GB indexes. The database has also approx 500 connections via toplink connection pools from 8 application servers.
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Oct 25, 2012
Redo log information can be transmitted in one of two ways from the primary database to the standby database: either by ARCH or LGWR.
1. when ARCH involves
2. when LGWR involves
FAL_Client = (Should i enter net service name or Db name or service_name
FAL_Server = Should i enter net service name or Db name or service_name )
FAL_CLIENT='whichone'
[code]...
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Jul 6, 2012
i am seeing (LGWR switch) happening in my databsae alert log every 3-4 minutes. is that appropriate? if not, what measure can i take to reduce this?
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Jun 30, 2010
I have configured data guard in the windows XP same server .It is not able to apply log to the Standby database.when I queried the following, I go the following erros..
sql>select message from v$dataguard_status where dest_id=2;
FAL[server, ARC0]: Error 12514 creating remote archivelog file 'STNDBY'
PING[ARCk]: Heartbeat failed to connect to standby 'STNDBY'. Error is 12528.
LGWR: I/O error 1089 archiving log 1 to 'STNDBY'
"ARCk: Attempting destination LOG_ARCHIVE_DEST_2 network reconnect (3113)
"
"ARCk: Destination LOG_ARCHIVE_DEST_2 network reconnect abandoned
"
PING[ARCk]: Error 3113 when pinging standby STNDBY.
"LNS: Closing remote archive destination LOG_ARCHIVE_DEST_2: 'STNDBY' (error 1089)
"
LGWR: Error 1041 closing archivelog file 'STNDBY'
************************************************
Also if
SQL> select sequence#,applied from v$archived_log;
query gives the following message----
SEQUENCE# APP
---------- ---
7 YES
5 NO
8 NO
9 NO
6 NO
10 NO
10 NO
11 NO
11 NO
12 NO
12 NO
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Jul 2, 2010
its possible to have multiple LGWR processes for a single database.If its possible how does the multiple processes write from redo log buffer to online redo log file.
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Mar 10, 2013
I have few queries regarding standby database.
1)On primary Database Standby Redo log is required for switchover and on standby database Standby Redo log is required for
--Real time Apply
--Maximum protection or Maximum availability
Am I correct?
2)My database is in Maximum Performance mode. I set up following entry on init.ora:
LOG_ARCHIVE_DEST_2='service=standby LGWR ASYNC'. My question is do I need to have STANDBY Redo log file on standby database in order to use LGWR transport (LGWR ASYNC)mode from primary? Without Standby redo log on standby database can it transport redo data from primary to standby using LGWR transport mode (LGWR ASYNC)?
3)I have changed from the "ARCH" attribute to "LGWR" attribute of the LOG_ARCHIVE_DEST_n initialization parameter. But I have not changed the protection mode. I would like to know whether is there any impact in the behavior of the database, if we do not change the mode from "MAXIMUM PERFORMANCE" to "MAXIMUM AVAILABILITY"?
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Oct 5, 2010
In statspack I find a lot of wait events "ARCH wait on SENDREQ". The database is configured with the LGWR ASYNC attribute. In the documentation I can read that the "ARCH wait"-events may happen in case the database is configured with the ARCH attribute.How is it possible I get these "ARCH wait"-envents and do these wait events have any effect on the "on line" performance of the database? Is it possible that a user that saves data in the database has to wait for thest "ARCH wait"-events?
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Jan 10, 2013
I am facing the row lock issue in production. I have been trying to resolve the issue but i coud'nt. I traced out by using different queries which sql query is locking which but everything looks good.
And i also checked for connections open and close everything is in good place but unable to resolve the issue. we are running a batch file which runs in every night some of the records are processing and if any one record is failed it is blocking another records.My oracle version is oracle 10.2.0
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Apr 12, 2010
I want to Who is locking the table by an SQL statement
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Sep 1, 2013
Say we have an employee(id_emp) table with a primary key on id_emp. We have also some history tables emp_stuff with columns say (id_emp, dat_event, some_stuff) with primary key id_emp, dat_event.
This means that we have a unique index on (id_emp,dat_event). We also have a foreign key id_emp that references employee(id_emp). When we update id_emp on employee, we still have a lock on emp_stuff. According to this (end of the page) :
Quote:So, in short, with releases prior to Oracle Database 11g Release 1, you will want an index on the foreign key of the child table if you do any of the following:
Update the parent table primary key
Delete from the parent table
Merge into the parent table
So is id_emp in emp_stuff considered as indexed (through the unique index of the primary key) or do we have to add an explicit index
like this CREATE INDEX emp_stuff ON emp_stuff(id_emp) to avoide child table locks?
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Oct 21, 2010
I have developed a form, containing 5 tab pages and also referencing to 5 tables.tab page a of table a some fields are required and some or not.when i open form and start entering record, and then i change mine and dont enter and want to navigate to some other page, it simply allows me to leave it blank and move to some other tab page.
tab page b of table bsome fields are required and some or not.when i open this tab page and one i click in the first field and then do not enter anything in it and want to leave it , it does not allow me to leave blank.what could be the reason. why one tab page allow me to leave blank and navigate and why the other does not?first field of both tab pages are required.
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Aug 27, 2013
11.2.0.1 I am still resolving the locking issues in our database Often the delete is blocked by some transaction. The operations said that it is intermittent. Last night they were able to delete the 1M transactions without the locking.But the past days lock often occurred, and they have to bounced the database to release the locks.
I there a way I can compare what happened last night why the batch was able to delete smoothly , and compare it against the other night where the delete was blocked?By using ASH, AWR, ADDM? I also run now this procedure, to identify the blocking sql statement:
SQL> exec dbms_workload_repository.add_colored_sql(sql_id => 'fn3qv2dhsu3nb');
PL/SQL procedure successfully completed.Can I now run AWR,ASH,ADDM, to identify/capture the sql being run?
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Aug 9, 2013
Using Oracle 11gr2. If I call the following update statement from session A, session A will lock the row until a commit/rollback statement is issued from session A. If session B calls the same update statement and same row, session B will have to wait until the lock is released in session A. However, the application developers are speaking in terms of threads. Could it be possible that the update statement is called within the same session by multiple requests? If yes, could the case statement be evaluated without the row being locked which could lead to false results? Trying to keep this post brief. tableA has columnA (primary key, number) and columnB (number)
{update tableAset columnB = case when columnB = 3 then 4 when columnB = 4 then 5 else columnB endwhere columnA = 6;}
Could 2 requests (almost at the exact same time) in the same session evaluate columnB as 3. The desired result would be the first request sets the column to 4 and the second request sets the column to 5.
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Dec 27, 2006
We have a table with several columns (id, title, description, area).The data in the table looks like this
1 sometitle1 description1 USA
2 sometitle2 description2 Germany
3 sometitle3 description3 Japan
4 sometitle4 description4 Honduras
We have Oracle users with their usernames and password. We would like to lock every single user to a certain area.Example:
user 1 may see only records, where AREA=USA
user 2 may see only records, where AREA=Honduras
How can I do this in Oracle. I am using Oracle Enterprise 9.2
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Nov 9, 2010
I am having a data guard setup done in oracle 10g(10.2.0.4.0) WINDOWS Platform. some of the archive process are locked in primary db side.
PROCESS STATUS LOG_SEQUENCE STAT
-------- ---------- ------------ ----
0 ACTIVE 0 IDLE
1 ACTIVE 804462 IDLE
2 ACTIVE 0 IDLE
3 ACTIVE 0 IDLE
4 ACTIVE 0 IDLE
5 ACTIVE 800011 BUSY
6 ACTIVE 0 IDLE
7 ACTIVE 800009 BUSY
8 ACTIVE 0 IDLE
9 ACTIVE 802335 BUSY
10 ACTIVE 0 IDLE
Shall we kill the locking archive processes? killing archive processes will cause any problem?
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May 26, 2013
I've a table TXN1 transaction and has FKs to 3 different tables Account, customer, country and currency. ALL FKs are indexed (bitmap). I am updating TXN1 of amount column about 10,000 rows. (SID 1) As expected, it has taken lock type 3 SX on TXN1. But it has taken on lock type 4 (share) on Account, customer and country. Committing every 10k rows.
At the same time sid 2 is inserting into another TXN2 table which has FK to the same dimensions account, customer and currency. Only FK on ac_id is bitmap indexed. The inserts have taken SX lock(type 3) on tXN2 table (expected). But it is trying to take SX type 3 lock on account, customer, currency tables. typ3 lock taken on CCY but waiting on CST. But It is blocked by sid 1. It has resulted into Enque-TM contention and resulted into anywhere 60-300 secs wait time..
I understand update/delete in parent table results into locking of SX of child tables and need the FKs to be indexed to avoid etc.
1. Why is SID1 taking shared lock on the parent tables Account,customer,country and currency tables? The update statement is not updating any of those FK columns nor referring them in where clause(if it matters!). Is it to ensure that the parent rows are not deleted?
2. Why is SID2 taking SX lock on the dimension tables? Why is it not taking RS lock type 2 on parent rows? Why is SID1 taking shared lock type 4, but not 2?
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Nov 10, 2011
I have a set of rows based on a complex view from multiple table.
I will be updating some of its columns from front-end . Is there any possible ways to lock those rows of data while updating and no other users can update it;
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Jun 11, 2012
I am a developer and not a DBA and I need to find th correct query to find the exact rowid of the record locked on a table. This is for a RAC database and locked record can be from the web form in oracle application server. When I try to get the correct row id, I get the following error:
ORA-01410 - Invalid row id For the criteria, the output is Dbms_Rowid.rowid_create(1, -1, 36, 7845, 0), why I get a -1 for the ROW_WAIT_OBJ#?
Additional Information: The lock type is DML and the lock mode is: Row Exclusive, the table is locked and the program is web oracle forms executing.
I am executing the query in Oracle Database 11g Enterprise Edition Release 11.1.0.7.0
How to accomplish getting the correct rowid? Below is the selection criteria I have:
select vs.inst_id,
vs.audsid audsid,
locks.sid sid,
[Code]....
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Jan 25, 2011
I am new to performance tuning. One procedure is blocking and another is locking it.
SQL> @glockers
Oracle OS
INSTANCE SID TY Usernam SERIAL# SPID Process LMODE REQUEST
---------- ------ -- ------- ---------- ------------ ------- ------------------------------------ ------------------------------------
[code]...
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Nov 1, 2011
I have been plagued by people logging into my database and making changes when a clone is in process.. Having said that ,I am looking to lock accounts and unlock them when I am done.
I envision my code looking something like this:
sqlplus -s / <<END
SET PAGESIZE 0
SET FEEDBACK OFF
SET VERIFY OFF;
set heading off;
spool /tmp/lockusers.sql
select 'alter user ' || username || ' account lock;' from dba_users where username not in (....) and not locked?;
spool off;
END;
sqlplus -s / <<END
@/tmp/lockusers.sql
END;
When it comes time to unlock the accounts I want to be able to unlock those accounts I previously locked and not all of them. Is there a query, I can use that can tell me when the accounts were locked or some other way about going about this so I dont unlock accounts that were locked prior to my lock script running?
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Sep 2, 2009
I have a "select ... into" in my PL/SQL and it doesn't retreive any data(I suppose just certain columns because if it doesn't retreive a row then the PL/SQL should throw an error) when there are many users accessing this table. It shouldn't be some table locking right? Because if it is, it should wait until the table is available then it will retreive data. Currently it just proceeds with the PL/SQL and selecting nothing in that query. what details should I look at to trace the cause of this problem.
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