To enable lock, specify a lock type (lock mode) and the resource-specific name in the OpenTP1 system. The following two lock modes are available:

Lock for reference (shared mode PR Protected Retrieve):

The UAP can only reference resources with lock specified. Other UAPs are permitted only to reference the resources.

Lock for update (exclusive mode EX EXclusive):

The UAP can reference and update resources with lock specified. Other UAPs are not permitted to reference or update the resources.

A resource cannot/can be shared depending on the contents of the lock modes in the following case:

• When an attempt is made to specify lock for the resource, lock has been specified for the resource by another UAP.

The table below shows whether a resource can be shared if lock has been specified for the resource by more than one UAP. If the resource cannot be shared, the following can be specified in the UAP:

• An error is returned, or the function waits until the resource is released.
  

  Table 4-13 Combinations of lock modes and resource sharing enabled/disabled

  Lock mode of UAP shutting down the resource	Lock mode of UAP requesting lock
  	Lock for reference (PR)	Lock for update (EX)
  Lock for reference (PR)	Can be shared.	Cannot be shared.
  Lock for update (EX)	Cannot be shared.	Cannot be shared.