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• The Lock Instruction is used to specify a number of job nodes for mutual exclusion to prevent such jobs from being executed in parallelparallel either in the same workflow or in different workflows.
• Mutual exclusion is based on Resource Locks, i.e. semaphores, that can be used either exclusively or that can be shared within the limits of their capacity.
  • Exclusive Resource Lock: only one Lock Instruction can hold the Resource Lock at any given time. Any further Lock Instructions that try to acquire the same Resource Lock have to wait.
  • Shared Resource Lock: the Resource Lock is assigned a limit capacity that can be shared by a number of Lock Instructions. Each Lock Instruction carries a weight that counts towards the Resource Lock's limitcapacity.
• Jobs that wait to acquire a Resource Lock do not consume resources such as CPU. Orders that wait for a Resource Lock are in a WAITING state, see JS7 - Order State Transitions.
• If a job within a Lock Instruction fails then the order is considered being failed. In this situation the Resource Lock is still in use by the Lock Instruction.
• Note that Lock Instructions can be nested in a workflow that acquires a number of Resource Locks. This adds complexity to your workflows that should be managed to prevent deadlocks and . It is recommended not to block a number of Resource Locks for a longer time by failed orders.

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This video explains how to limit parallel execution for of jobs in a workflow.

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