topic Re: select single for update *...what does it do? in Application Development and Automation Discussions

select single for update *...what does it do?

dev_parbutteea — Wed, 26 Mar 2008 13:58:42 GMT

Hi .

In a standard program, a timeout is occuring because of this statement:

SELECT SINGLE FOR UPDATE * FROM NRIV WHERE

OBJECT = NRIV-OBJECT

AND SUBOBJECT = NRIV-SUBOBJECT

AND NRRANGENR = NRIV-NRRANGENR

AND TOYEAR = NRIV-TOYEAR.

When i checked the table NRIV, there were only 2000 entries in it.There is only 1 row which corresponds to the condition.This leads me to believe that the select single for update * is causing the timeout and not the volume of the db table.

What exactly does it mean and how can i correct it?

Re: select single for update *...what does it do?

Former Member — Wed, 26 Mar 2008 14:05:48 GMT

Hi,

Check the Index settings of Table with ur BASIS team might be due to incorrect index which could cause TIMEOUT dump.

Regards,

Balakumar.G

Reward Points if helpful.

Re: select single for update *...what does it do?

former_member194669 — Wed, 26 Mar 2008 14:10:19 GMT

Hi,

The DB lock created from a SELECT SINGLE FOR UPDATE will be released only after a COMMIT WORK.

Please check in SM12

a®

Re: select single for update *...what does it do?

Former Member — Wed, 26 Mar 2008 14:12:40 GMT

Hello,

The 'FOR UPDATE' addition on the SELECT will set write protection for NRIV. Anytime a table needs to be locked there is the possibility that two or more processes will be fighting for that table at the same time. This could cause the timeout in your case and eventually a deadlock.

Hope that helps a little.

Regards

Greg Kern

Re: select single for update *...what does it do?

Former Member — Wed, 26 Mar 2008 14:15:50 GMT

An exclusive lock can be set for this line using the FOR UPDATE addition when a single line is being read with SINGLE. The SELECT command is used in this case only if all primary key fields in logical expressions linked by AND are checked to make sure they are the same in the WHERE condition. Otherwise, the resulting set is empty and sy-subrc is set to 8. If the lock causes a deadlock, an exception occurs. If the FOR UPDATE addition is used, the SELECT command circumvents SAP buffering.

Regards,

Santosh