tcl.unlock-item

clears item locks that have not cleared through usual system operation.

Item locks are set by Pick/BASIC 'read' statements and other mechanisms.

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

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.

A 'locked' clause in 'read' statements allows a graceful means of dealing with the situation of attempting to access a locked item. The program can take a special case and indicate to the operator that they should 'try again later.'

When a process attempts to access an item that is locked, the screen simply freezes and starts 'beeping'. Usually, there is only a brief wait until the item is unlocked, at which time the terminal stops beeping and is granted access to the item.

Other times, however, the locking system does not unlock the item for whatever reason (aborts, programming errors, logoffs, bad karma, etc.). It is in cases such as this, and only in these cases, that this verb should be used.