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# PetscViewerBinarySetFlowControl
Sets how many messages are allowed to be outstanding at the same time during parallel IO reads/writes 
## Synopsis
```
#include "petscviewer.h"   
PetscErrorCode PetscViewerBinarySetFlowControl(PetscViewer viewer, PetscInt fc)
```
Not Collective


## Input Parameters

- ***viewer -*** `PetscViewer` context, obtained from `PetscViewerBinaryOpen()`
- ***fc -*** the number of messages, defaults to 256 if this function was not called





## See Also
 [](sec_viewers), `PETSCVIEWERBINARY`, `PetscViewerBinaryOpen()`, `PetscViewerBinaryGetInfoPointer()`, `PetscViewerBinaryGetFlowControl()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/classes/viewer/impls/binary/binv.c.html#PetscViewerBinarySetFlowControl">src/sys/classes/viewer/impls/binary/binv.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/tutorials/ex10.c.html">src/vec/vec/tutorials/ex10.c</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/classes/viewer/impls/binary/binv.c.html#PetscViewerBinarySetFlowControl_Binary">PetscViewerBinarySetFlowControl_Binary in src/sys/classes/viewer/impls/binary/binv.c</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/sys/classes/viewer/impls/binary/binv.c)


[Index of all Viewer routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)