Change control is used in Application Designer to lock definitions and track history changes for each object. Change control can be activated through Application Designer using Tools > Change Control > Administrator.
After few good size projects, you can easily have hundreds if not thousands of locked objects. Attempting to unlock the objects one by one is very time consuming, so here is a way to speed up the process.
Locked objects are stored on PSCHGCTLLOCK table. Here is how PeopleSoft describes the table: