DB2® Universal Database™ for OS/390™ v7.1 Application Certification Guide

Locking Data

DB2 uses transaction locking (via the IRLM—Internal Resource Lock Manager), latches, and other non-IRLM mechanisms to control concurrency and access of SQL statements and utilities. These mechanisms are there to associate a resource with a process so that other processes cannot access the same resource when it would cause lost updates and access to uncommitted data. Generally, a process will hold a lock on manipulated data until it has completed its work. This way it ensures that other processes do not get hold of data that has been changed but not committed. Another use is for repeatable read, when an application has the need to reread data that must still be in the same state as it was when it was initially read. There are also ...