Oracle for update no wait

Hi All..
Can any one pls tell me in which case we need to use for update no wait in cursors.
my understanding is for enable locks on top of records selected by cursor using for update.
but dont have knowlodge on NOWAIT clause.Can any one pls tell me in which case exactly we have to use nowait clause .
Thanks in advance,
Sanjeev.

Hi Sanejev,
There are 3 choices
1. NOWAIT, You will set this, if you don't want to wait for the locks.
Enough if 1 row is not available for you, you will get a ORA-54.
2. You can wait up to 'n' seconds. after 'n' seconds you haven't got the rows
you will get an ORA-30006.
3. New feature - offically- in Oracle 11g! SKIP LOCKED!
Sometimes is good for us that we TRY to lock all the rows, but no problem if there are some rows
which are available for us.
In this case we modify all availabe rows the remaining will be skipped.
Later - maybe- we try to repeat our process for the remaining rows.
Of course, we mark our modified rows somehow(for example with flag)
Note that this feature is available in Oracle 10g( unofficially)!
Best regards
Laszlo
(SQL and PL/SQL trainer in Hungary)

Similar Messages

Select for update no wait distributed polling strategy

I have an esb process which currently uses 'logicaldeletepolling strategy'.
I need to change it to use the 'select for update no wait' distributed polling strategy.
What steps do I need to perform on the existing process ?

Hi,
Try: http://download-east.oracle.com/docs/cd/B31017_01/integrate.1013/b28994/adptr_db.htm#sthref558 (Oracle® Application Server Adapters for Files, FTP, Databases, and Enterprise Messaging User's Guide
10g Release 3 (10.1.3.1.0)
Part Number B28994-02).
Also you can reconfigure DB adapter (I think this's the best way): laucnch adapter configuration wizard in JDev and at step 9 (adapter options) check distributed polling checkbox (query now contains for update clause).

Hi Select for update no wait

Hi All
please anybody help me with an ex of select for update no wait.
my requirement is i want to update one table , before updating i want to know is that table is using by some other.

What do you mean by
same record is opened Do you mean, queried by another form? This is not possible.... other session can always query a table (with approp privs)
You are confusing me....
1) you update DEPT using a form (not clear which one - but it is irrelevant)
2) Another form is querying the DEPT table and you want to know this? Why? What do you care?
If you are worried about a lost update, don't... Forms takes care of this

Select for update no wait polling strategy for an esb process

I have an esb process which currently uses 'logicaldeletepolling strategy'.
I need to change it to use the 'select for update no wait' distributed polling strategy.
What steps do I need to perform on the existing process ?

What do you mean by
same record is opened Do you mean, queried by another form? This is not possible.... other session can always query a table (with approp privs)
You are confusing me....
1) you update DEPT using a form (not clear which one - but it is irrelevant)
2) Another form is querying the DEPT table and you want to know this? Why? What do you care?
If you are worried about a lost update, don't... Forms takes care of this

"SELECT .. FOR UPDATE" lock event

Hi All,
The application will send "SELECT .. FOR UPDATE" statement when end-user click one module on screen.
Now the system have many end-user need to use this module more than before and elapsed time is 15 seconds per session if have 10 sessions click this module that mean the maximum locked time is 150 seconds (15*10) and source code cannot change.
My question is which oracle parameter can control about lock timeout in this case or not?
I tried to check all parameter about lock and timeout of oracle parameter that cannot to solve it but I may missing something.
Thansks
Hiko

taohiko wrote:
Hi All,
The application will send "SELECT .. FOR UPDATE" statement when end-user click one module on screen.
Now the system have many end-user need to use this module more than before and elapsed time is 15 seconds per session if have 10 sessions click this module that mean the maximum locked time is 150 seconds (15*10) and source code cannot change.
My question is which oracle parameter can control about lock timeout in this case or not?
I tried to check all parameter about lock and timeout of oracle parameter that cannot to solve it but I may missing something.
Thansks
Hikohttp://download.oracle.com/docs/cd/E11882_01/appdev.112/e17126/static.htm#LNPLS603
By default, the SELECT FOR UPDATE statement waits until the requested row lock is acquired. To change this behavior, use the NOWAIT, WAIT, or SKIP LOCKED clause of the SELECT FOR UPDATE statement.
If you are adamant as you say that the application cannot be changed (almost never a truthful statement) ... then you are out of luck.

Database select for update locks ADF

Hi,
When a user has initiated an update session in an adf application and locking is optimistic it will acquire a lock on table row using select for update no wait; . But when the user closes a tab the session would not be terminated. Now i know as HTTP is a stateless protocol, we can wait for the timeout and then the lock will be released using a session listener implementation. But if the user instead tries to log in again in a new tab and tries to edit the same record he will receive a message stating that another user already holds a lock on the record which is correct, but is misleading.
So can we rely on javascript for these scenarios that as soon as the user closes the tab the session should be terminated.
Here's a snippet
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/dojo/1.4/dojo/dojo.xd.js" ></script>
<script type="text/javascript">
var unLoad = function() {
    dojo.io.script.get({
    url:'http://127.0.0.1:7101/myapp/adfAuthentication?logout=true',
    timeout:15000,
dojo.addOnWindowUnload(unLoad);
</script>I know this might not work always as it depends on the fact that request might / might not be processed by the server.
Are there any alternate solutions and also reducing the session timeout is ruled out in my scenario.

Ramandeep,
So are there other alternatives or solutionsAlternatives or solutions to what, exactly? As Jobinesh has told you, as long as you use optimistic locking, ADF doesn't acquire database locks except in the context of a transaction that is going to be completed in the current HTTP request. You could obviously force ADF to deviate from this if you called "postChanges" during an HTTP request and leave the transaction hanging, but that would just be wrong in an optimistic locking scenario - the solution would be "don't do that."
John

Select for update gives wrong results. Is it a bug?

Hi,
Select for update gives wrong results. Is it a bug?
CREATE TABLE TaxIds
TaxId NUMBER(6) NOT NULL,
LocationId NUMBER(3) NOT NULL,
Status NUMBER(1)
PARTITION BY LIST (LocationId)
PARTITION P111 VALUES (111),
PARTITION P222 VALUES (222),
PARTITION P333 VALUES (333)
ALTER TABLE TaxIds ADD ( CONSTRAINT PK_TaxIds PRIMARY KEY (TaxId));
CREATE INDEX NI_TaxIdsStatus ON TaxIds ( NVL(Status,0) ) LOCAL;
Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100101, 111, NULL);
Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100102, 111, NULL);
Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100103, 111, NULL);
Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100104, 111, NULL);
Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (200101, 222, NULL);
Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (200102, 222, NULL);
Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (200103, 222, NULL);
--Session_1 return TAXID=100101
select TAXID from TAXIDS where LOCATIONID=111 and NVL(STATUS,0)=0 AND rownum=1 for update
--Session_2 waits commit
select TAXID from TAXIDS where LOCATIONID=111 and NVL(STATUS,0)=0 AND rownum=1 for update
--Session_1
update TAXIDS set STATUS=1 Where TaxId=100101;
commit;
--Session_2 return 100101 opps!?
--Session_1 return TAXID=100102
select TAXID, STATUS from TAXIDS where LOCATIONID=111 and NVL(STATUS,0)=0 AND rownum=1 for update
--Session_2 waits commit
select TAXID, STATUS from TAXIDS where LOCATIONID=111 and NVL(STATUS,0)=0 AND rownum=1 for update
--Session_1
update TAXIDS set STATUS=1 Where TaxId=100102;
commit;
--Session_2 return 100103

This is a bug. Got to be a bug.
This should be nothing to do with indeterminate results from ROWNUM, and nothing to do with read consistency at the point of statement start time in session2., surely.
Session 2 should never return 100101 once the lock from session 1 is released.
The SELECT FOR UPDATE should restart and 100101 should not be selected as it does not meet the criteria of the select.
A statement restart should ensure this.
A number of demos highlight this.
Firstly, recall the original observation in the original test case.
Setup
SQL> DROP TABLE taxids;
Table dropped.
SQL>
SQL> CREATE TABLE TaxIds
2 (TaxId NUMBER(6) NOT NULL,
3   LocationId NUMBER(3) NOT NULL,
4   Status NUMBER(1))
5 PARTITION BY LIST (LocationId)
6 (PARTITION P111 VALUES (111),
7   PARTITION P222 VALUES (222),
8   PARTITION P333 VALUES (333));
Table created.
SQL>
SQL> ALTER TABLE TaxIds ADD ( CONSTRAINT PK_TaxIds PRIMARY KEY (TaxId));
Table altered.
SQL>
SQL> CREATE INDEX NI_TaxIdsStatus ON TaxIds ( NVL(Status,0) ) LOCAL;
Index created.
SQL>
SQL>
SQL> Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100101, 111, NULL);
1 row created.
SQL> Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100102, 111, NULL);
1 row created.
SQL> Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100103, 111, NULL);
1 row created.
SQL> Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (100104, 111, NULL);
1 row created.
SQL> Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (200101, 222, NULL);
1 row created.
SQL> Insert into TAXIDS (TAXID, LOCATIONID, STATUS) Values (200102, 222, NULL);
1 row created.
SQL> commit;
Commit complete.
SQL> Original observation:
Session1>SELECT taxid
2 FROM   taxids
3 WHERE locationid    = 111
4 AND    NVL(STATUS,0) = 0
5 AND    ROWNUM        = 1
6 FOR UPDATE;
     TAXID
    100101
Session1>
--> Session 2 with same statement hangs until
Session1>BEGIN
2   UPDATE taxids SET status=1 WHERE taxid=100101;
3   COMMIT;
4 END;
5 /
PL/SQL procedure successfully completed.
Session1>
--> At which point, Session 2 returns
Session2>SELECT taxid
2 FROM   taxids
3 WHERE locationid    = 111
4 AND    NVL(STATUS,0) = 0
5 AND    ROWNUM        = 1
6 FOR UPDATE;
     TAXID
    100101
Session2>There's no way that session 2 should have returned 100101. That is the point of FOR UPDATE. It completely reintroduces the lost UPDATE scenario.
Secondly, what happens if we drop the index.
Let's reset the data and drop the index:
Session1>UPDATE taxids SET status=0 where taxid=100101;
1 row updated.
Session1>commit;
Commit complete.
Session1>drop index NI_TaxIdsStatus;
Index dropped.
Session1>Then try again:
Session1>SELECT taxid
2 FROM   taxids
3 WHERE locationid    = 111
4 AND    NVL(STATUS,0) = 0
5 AND    ROWNUM        = 1
6 FOR UPDATE;
     TAXID
    100101
Session1>
--> Session 2 hangs again until
Session1>BEGIN
2   UPDATE taxids SET status=1 WHERE taxid=100101;
3   COMMIT;
4 END;
5 /
PL/SQL procedure successfully completed.
Session1>
--> At which point in session 2:
Session2>SELECT taxid
2 FROM   taxids
3 WHERE locationid    = 111
4 AND    NVL(STATUS,0) = 0
5 AND    ROWNUM        = 1
6 FOR UPDATE;
     TAXID
    100102
Session2>Proves nothing, Non-deterministic ROWNUM you say.
Then let's reset, recreate the index and explicity ask then for row 100101.
It should give the same result as the ROWNUM query without any doubts over the ROWNUM, etc.
If the original behaviour was correct, session 2 should also be able to get 100101:
Session1>SELECT taxid
2 FROM   taxids
3 WHERE locationid    = 111
4 AND    NVL(STATUS,0) = 0
5 AND    taxid         = 100101
6 FOR UPDATE;
     TAXID
    100101
Session1>
--> same statement hangs in session 2 until
Session1>BEGIN
2   UPDATE taxids SET status=1 WHERE taxid=100101;
3   COMMIT;
4 END;
5 /
PL/SQL procedure successfully completed.
Session1>
--> so session 2 stops being blocked and:
Session2>SELECT taxid
2 FROM   taxids
3 WHERE locationid    = 111
4 AND    NVL(STATUS,0) = 0
5 AND    taxid         = 100101
6 FOR UPDATE;
no rows selected
Session2>Of course, this is how it should happen, surely?
Just to double check, let's reintroduce ROWNUM but force the order by to show it's not about read consistency at the start of the statement - restart should prevent it.
(reset, then)
Session1> select t.taxid
2   from
3    (select taxid, rowid rd
4      from   taxids
5      where locationid = 111
6      and    nvl(status,0) = 0
7      order by taxid) x
8   , taxids t
9   where t.rowid = x.rd
10   and   rownum = 1
11   for update of t.status;
     TAXID
    100101
Session1>
--> Yes, session 2 hangs until...
Session1>BEGIN
2   UPDATE taxids SET status=1 WHERE taxid=100101;
3   COMMIT;
4 END;
5 /
PL/SQL procedure successfully completed.
Session1>
--> and then
Session2> select t.taxid
2   from
3    (select taxid, rowid rd
4      from   taxids
5      where locationid = 111
6      and    nvl(status,0) = 0
7      order by taxid) x
8   , taxids t
9   where t.rowid = x.rd
10   and   rownum = 1
11   for update of t.status;
     TAXID
    100102
Session2>Session 2 should never be allowed to get 100101 once the lock is released.
This is a bug.
The worrying thing is that I can reproduce in 9.2.0.8 and 11.2.0.2.

For Update Query with Wait Clause from ORACLE Forms

Hi
We are using Oracle Forms 10g running with 10g database 10.2.0.1.0. We happend to see a query which is getting generated in AWR report like Select rowid, all_columns from TableName for Update of C1 Nowait. But no such query is really written in forms and we are aware that, Any query prefixed with rowid is definitely executing from Forms. But how the ForUpdate and Nowait clause is appended to the query.
We have checked the following properties in the database Block
*1) Locking Mode is set to Automatic*
*2) Update Changed Columns only is set to YES*
*3) Query all records is set to No (Though this particular property may not be relevant to the issue)*
What is the property or setting which might trigger such a query from ORACLE Forms with ForUpdate and Nowait clause.
Any ideas/suggestions on why such behaviour. Please have a healthy discussion on this. Thanks in advance.

Why have you started another thread on the same thing?
FOR UPDATE cursor is causing Blocking/ Dead Locking issues
Just use one thread to avoid confusion.
The fact that nobody has answered on the other thread for a couple of days could be to do with it being the weekend and most people are not at work.
Either be patient or, if it's more "urgent" than that, raise a SR/Tar with Oracle metalink.

"FRM-40501: Oracle error: Unable to Reserve Record For Update or Delete"

"FRM-40501: Oracle error: Unable to Reserve Record For Update or Delete"
as I can unblock a session in the graphical surroundings of administration of the BD 10g of Oracle

From experience with this problem since the blocked customer form has been coded not to wait for the updating session to complete then there is likely no waiter on the system now so you cannot find the blocking session.
What you need to do is determine what row the Form was going after then using SQLPlus issue an update on the row. If the blocking session has not yet committed then this update will wait. Now if you look for blocking sessions you will be able to find it and make a determination if the session should be killed or if someone needs to call the user and ask he or she to flip through their screens and get out of the blocking screen.
Applications screens written not to wait on currently being updated data need to also be written to expose the information necessary to identify the row(s) in question.
HTH -- Mark D Powell --

Oracle select for update: not releasing lock

My JDBC code uses "select for update" to modify record in Oracle database. I tried to simulate network connection down situation.
After my JDBC code locked on a record using "select for update", I unplugged the network cable. I then tried to run the same code on another computer, but it could not accquire the lock, because the previous lock was not released. I tried sqlplus to lock the record, but failed also. The lock has been there for at least an hour now. I guess it may finally be released, but is there a way for oracle to release the lock as soon as the connection is down? Not know if it is a JDBC setting or oracle setting.

Dear Friend,
What you are trying to do is not correct way of checking the concurrency and transaction.
The reason is as listed below.
01.Always remember http is a stateless protocol and removing the connection or just closing the browser will never be informed to the database or to the application server thus the transaction monitor (TM)or processor will never release the lock as it will deem that the actor is manipulating the data.
02.As per locking goes every database is having a �TM� and the default isolation level setting is different like oracle uses serializable DB2udb 7.0 or db2/As400 uses repeatable read. You can change this setting by editing the default setting in the database but be very sure before touching it.
03. You can also transpose this with your Application server setting for that piece of code or Globally but again be very sure about it as it will change the entire gamete.
04. For releasing lock you have to manually do it or you can change the settings of App server or the Database to release the connection after some wait time.
Regards,
Ruchir

SELECT for update + WAIT: why this doesn't work?

here is sample data:
create table t1 (x number, y number);
create table t2 (x number, y number);
insert into t1 values(1,1);
insert into t1 values(2,2);
insert into t1 values(3,3);
insert into t2 values(2,2);
commit;
session 1:
update t1 set y = 20 where x = 2; -- do not commit here
session 2:
declare
cursor c is ( select t1.rowid as t1rid, t2.x, t2.y
from t1, t2
where t1.x = t2.x ) for update wait 300;
type c_t is table of c%rowtype;
c_v c_t;
begin
open c;
loop
    fetch c bulk collect into c_v;
    exit when c%notfound;
    forall i in 1..c_v.count
      update t1 set y = 40 where rowid = c_v(i).t1rid;
end loop;
close c;
end;now session 2 waits because the row is locked in session 1. do a rollback in session 1. session 2 continues but doesn't update a row. why?
thank you

943276 wrote:
thanks!
I followed your remarks and found this interesting article:
http://www.oracle.com/technetwork/issue-archive/2008/08-mar/o28plsql-095155.html
I have to re-read it again and give it a second thought but I grasped the idea. so, if there is no LIMIT clause this code should be OK, right?
open c;
fetch c bulk collect into c_v;
forall i in 1..c_v.count
update t1 set y = 40 where rowid = c_v(i).t1rid;
close c;
You are absolutely right, now..
while when I decide to process in "batches" this one should stay, right?
open c;
loop
fetch c bulk collect into c_v limit 1000;
exit when c_v.count = 0;
forall i in 1..c_v.count
update t1 set y = 40 where rowid = c_v(i).t1rid;
end loop;
close c;
This also looks fine.. (Hopefully, you are just learning..the samething can be done with a single UPDATE
my concern is that I don't understand the way WAIT works when incorporated in above scenario. is it:
a) delaying opening a cursor for declared time (max) or untill the lock can be placed on all rows? ORThis is what is happening..
b) cursor opens anyway, it is bulk update which is waiting OR
c) something else?
could you please in a few words describe what is happening within the scenario above with two sessions?
thank you

Whether two session with for update at the same time will wait for another?

Will this scenario happen?
One session executes: select ... for update/select ... for update nowait
The other session also executes: select ... for update/select ... for update nowait
Two sessions happens at the same time unluckily. Whether they will all stand by because of "for update" or quit immediately because of "nowait"?
Thx a lot.

HiddenName wrote:
This situation is called 'a deadlock'. Oracle will automaticaly detect a deadlock. One of the statements will fail with ORA-00060 deadlock detected;
No, it's not.
A deadlock is when sesson-A has a lock on something that session-B needs in order to continue, and at the same time, session-B has a lock on something that Session-A needs in order to continue. They BOTH have something the other needs.
In the OP's case, at least as he described it, it is simple serialization. The one with the lower scn will go, then the next.
PS.
Why don't you try? You can setup a small table with some records, open 2 sessions to the same database and for example issue UPDATE statements:
session 1: update where id=1
session 2: update where id=2
session 1: update where id=2 - this will hang waiting for session 2 to commit and free lock
session 2: update where id=1 - ORA-00060
You may also read about deadlocks in chapter on "Data Concurency and Consistency" of "Oracle Concepts'.

Difference in select for update of - in Oracle Database 10g and 11g

Hi, I found out that Oracle Database 10g and 11g treat the following PL/SQL block differently (I am using scott schema for convenience):
DECLARE
  v_ename bonus.ename%TYPE;
BEGIN
  SELECT b.ename
    INTO v_ename
    FROM bonus b
    JOIN emp e ON b.ename = e.ename
    JOIN dept d ON d.deptno = e.deptno
   WHERE b.ename = 'Scott'
     FOR UPDATE OF b.ename;
END;
/While in 10g (10.2) this code ends successfully (well NO_DATA_FOUND exception is raised but that is expected), in 11g (11.2) it raises exception "column ambiguously defined". And that is definitely not expected. It seems like it does not take into account table alias because I found out that when I change the column in FOR UPDATE OF e.empno (also does not work) to e.mgr (which is unique) it starts working. So is this some error in 11g? Any thoughts?
Edited by: Libor Nenadál on 29.4.2010 21:46
It seems that my question was answered here - http://stackoverflow.com/questions/2736426/difference-in-select-for-update-of-in-oracle-database-10g-and-11g

The behaviour seems like it really is a bug and can be avoided using non-ANSI syntax. (It makes me wonder why Oracle maintains two query languages while dumb me thinks that this is just a preprocessor matter and query engine could be the same).

Good day. as I can do to update my iphone 4 to the latest version of ios 5. whenever you connect to the pc and try to update the waiting time is very long, sometimes up to 12 hours and despite the wait always produce an error message for a long time waiti

good day. as I can do to update my iphone 4 to the latest version of ios 5. whenever you connect to the pc and try to update the waiting time is very long, sometimes up to 12 hours and despite the wait always produce an error message for a long time waiting

Disable ALL security software (firewall, antivirus/spyware, etc.) running on your PC while updating.

I updated my ipod touch, then a while later it said waiting for update then shut off. then started turning on and off, what do i do ?

I updated my ipod touch, then a while later it said waiting for update then shut off. then started turning on and off, what do i do ?

Try:
- iOS: Not responding or does not turn on
- Also try DFU mode after try recovery mode
How to put iPod touch / iPhone into DFU mode « Karthik's scribblings
- If not successful and you can't fully turn the iOS device fully off, let the battery fully drain. After charging for an least an hour try the above again.
- If still not successful that usually indicates a hardware problem and an appointment at the Genius Bar of an Apple store is in order.
Apple Retail Store - Genius Bar

Oracle for update no wait

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