tcl.basic-prot

toggles or displays the status of the Pick/BASIC object protection scheme.
When enabled, this feature is global, thus it affects the entire system.

The Pick System shares Pick/BASIC object code between all processes running a given program. While this vastly decreases memory requirements, it also opens the possibility of one user compiling a program while another user is concurrently running that same routine. This circumstance tends to produce random, unexplainable aborts that can be difficult to track on large systems. The protection scheme involves insulating running object code from updates caused by recompilation.

When protection is enabled, all previous revisions of Pick/BASIC object code are kept in the same dictionary group, but are simply marked as 'deleted'. These 'deleted' items are automatically cleared during the 'save' process. (See the discussion of 'dirty bits' in the topic on the 'save' verb.) This allows compiling programs while they are currently being executed. Users running a given program when that program is compiled will continue to run the old version. If a user drops out of the program, to TCL, for example, and re-executes the program, the system will execute the newest object version.