Jean Pierre--
When you use the
VISA Lock Async.vi to
lock a resource, operations invoked by other sessions to the same
resource are serviced or returned with a locking error, depending on
the operation and the type of lock used.
If a session has an exclusive lock, other sessions cannot modify global
attributes or invoke operations, but can still get attributes and set
local attributes. If the session has a shared lock, other sessions that
have shared locks can also modify global attributes and invoke
operations. Regardless of which type of lock a session has, if the
session is closed without first being unlocked, VISA automatically
performs a viUnlock() on that session.
The locking mechanism works for all processes and resources existing on
the same computer. When using remote resources, however, the
networking protocol may not provide the ability to pass lock requests
to the remote device or resource. In this case, locks will behave as
expected from multiple sessions on the same computer, but not
necessarily on the remote device. For example, when using the VXI-11
protocol, exclusive lock requests can be sent to a device, but shared
locks can only be handled locally.
Mark
