# Parallel sub-process executions

**URL:** <https://forum.flowable.org/t/parallel-sub-process-executions/1776>\
**Category:** Flowable Engine\
**Created:** [March 21, 2018, 5:37am UTC](https://forum.flowable.org/t/parallel-sub-process-executions/1776 "2018-03-21T05:37:49Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![enchobelezirev](https://yyz1.discourse-cdn.com/flex035/user_avatar/forum.flowable.org/enchobelezirev/32/604_2.png) [@enchobelezirev](https://forum.flowable.org/u/enchobelezirev)\
**Post date:** [March 21, 2018, 5:37am UTC](https://forum.flowable.org/t/parallel-sub-process-executions/1776/1 "2018-03-21T05:37:49Z")

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Hello,

I have a BPMN diagram in which I want to start a multi-instance CallActivity by providing the collection which need to be iterated and the name of the iterationVariable. I need all elements from the collection to be executed in parallel sub-processes.  
Could you suggest me how to achieve that?

I have read about an OptimisticLockingException during such scenario. Could you tell me whether the scenario will work now?

Regards,  
Encho

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**Author:** ![tijs](https://avatars.discourse-cdn.com/v4/letter/t/bc79bd/32.png) [@tijs](https://forum.flowable.org/u/tijs)\
**Post date:** [March 22, 2018, 2:14pm UTC](https://forum.flowable.org/t/parallel-sub-process-executions/1776/2 "2018-03-22T14:14:46Z")

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Hi Encho,

Like described in the documentation for multi instance constructs you can use something like:

flowable:collection="${myService.resolveUsersForTask()}" flowable:elementVariable=“assignee”

These are attributes you can add to the callActivity element or you could use a multi instance embedded subprocess with the call activity inside it instead.

It should be fine using this approach.

Best regards,

Tijs

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<div class="post-metadata">

**Author:** ![enchobelezirev](https://yyz1.discourse-cdn.com/flex035/user_avatar/forum.flowable.org/enchobelezirev/32/604_2.png) [@enchobelezirev](https://forum.flowable.org/u/enchobelezirev)\
**Post date:** [March 23, 2018, 6:29am UTC](https://forum.flowable.org/t/parallel-sub-process-executions/1776/3 "2018-03-23T06:29:49Z")

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Hello Tijs,

Thanks for the response.  
I think that somewhere I came across a topic which was related to a bug(missing feature) in the CallActivity which was preventing the parallel execution. Do you know of something like that?

Thanks,  
Encho