UNABLE_TO_LOCK_ROW, unable to obtain exclusive access to this record

Question

I have a batch process which updates Accounts and sometimes when i run this batch i get the error.

UNABLE_TO_LOCK_ROW, unable to obtain exclusive access to this record

I did read through Mohit's answer on why this is happening here Can anybody explain the UNABLE_TO_LOCK_ROW error?

Based on this article http://www.salesforce.com/us/developer/docs/apexcode/Content/langCon_apex_locking_statements.htm

Using the FOR UPDATE locks the whole set of records. The question i have is that is it a good practice to do this on a batch process, as the batch process could run for sometime and till then all the records would be locked.

In my batch process i am querying for all the accounts in the start method and in the execute method i am checking for certain conditions deciding if these records need to be updated or not. I cant perform these checks using WHERE clause as it depends on combination of factors dependent on other objects.

Answer 1

FOR UPDATE has to be written and that would avoid the error.Only record that batch context will process will be locked for very minimal amount of time .

Only those on which DML will happen at current time will be locked so prefer using FOR UPDATE keyword