Lock on the same record and diff record ?

[roy shao]

hi,
if client A modified record No.1, and client B also modified record No.1, the B should be blocked,
and if Client B is modifying not record No.1, such as record No.2, then client B need not be blocked ?
is my understanding correct ? please clear my idea about it.
Thank you !
Roy

[ruilin yang]

Yes, You are right. This is so called "horirontal lock" scheme, which is more effecient.

[roy shao]

thanks, then i will wonder this: if record No.1 lock and No2 lock is not mutex, at the file I/O level, when write to file, need thread safe ? i.e. write to No1, No.2 record at same time will bring any problem ?