tcl.unlock-group

clears group locks.

This is capable of clearing all types of group locks or specific types of locks, such as: update group locks, retrieval group locks, or locks on file control blocks.

Group locks provide a means of assuring data reliability by preventing two processes from attempting to update the same group at the same time.

Many processes within the system set group locks. For instance, the 'save' processor locks a group while it is being saved.

The 'read' statements (in Pick/BASIC) that have a 'locking' form set 'item' locks only while working with an item. This means that two processes can access items in the same group, provided they do not attempt to update the same item. This is in contrast to early Pick systems, which only set group locks on 'read' statements. The 'locked' clause in the 'read' statements allow a graceful means of dealing with the situation of attempting to access a locked item. The program can take a special path and indicate to the operator that they should 'try again later.'