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Using Queues to Lock and Unlock UnitsLocate this document in the navigation structure

Use

Units are always locked and unlocked when the COMMIT WORK is performed.

Procedure

Using the classes CL_QRFC_LOCK_INBOUND, CL_QRFC_LOCK_OUTBOUND and CL_QRFC_LOCK_NOSEND, you can use queue locks to prevent the processing of units, and you can also cancel a queue lock.

Example
Figure 1: Graphic: Lock Methods
Result

  • The LOCK_QUEUE_FROM_TOP method locks the first unit at the beginning of the specified queue for a destination. This makes it possible to lock a queue retroactively. If no unit exists, an empty unit is created automatically to map the lock.

  • The LOCK_QUEUE_FROM_CURRENT_POS method locks the execution of the next unit, which is written to the specified queue for a destination. This makes it possible to lock a queue preemptively. An empty unit is created to map the lock.

  • All queue locks become active at the next COMMIT WORK. If both unit locks as well as queue locks are created within an application LUW, then the queue locks are always set first and then the unit locks are assigned to the appropriate queues. For an illustration, see the following example:

Example

Operation on the Queue

Content of the Queue

Creation of Unit 1

Creation of Unit 2

COMMIT WORK

Unit 1 - Unit 2

Creation of Unit 3

Setting of lock A at current position

COMMIT WORK

Unit 1 - Unit 2 - Lock A - Unit 3

Setting of lock B at the beginning

Processing of unit 1 by the scheduler

Unit 2 - Lock A - Unit 3

COMMIT WORK

Lock B - Unit 2 - Lock A - Unit 3