Sharing Files on Multi-user Systems

The run-time system supports this COBOL system's multi-user facilities which allow files to be shared between users in a multi-user environment, and allow run-time system elements accessing those files to lock records or entire files in order to prevent access to them while data is being updated.

In single-user environments the multi-user syntax has no effect at run time, but run-time system elements can be developed for use in both single- and multi-user environments.

Files are either active or inactive. An active file is open to one or more run units. An inactive file is one that is not open to any run unit.

Active files can be open in one of two modes: exclusive or shareable:

The organization of the file affects the way the file can be shared:

Each run unit that is sharing access to a file can be locking either a single record or multiple records in that file. A run unit cannot select single record locking and multiple record locking for the same file.