# How to append output to XDMF file in a time-series simulation?

**URL:** https://discourse.vtk.org/t/how-to-append-output-to-xdmf-file-in-a-time-series-simulation/1066
**Category:** Support
**Created:** [June 2, 2019, 2:27pm UTC](https://discourse.vtk.org/t/how-to-append-output-to-xdmf-file-in-a-time-series-simulation/1066 "2019-06-02T14:27:02Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![amit112amit](https://discourse.vtk.org/user_avatar/discourse.vtk.org/amit112amit/32/2094_2.png) [@amit112amit](https://discourse.vtk.org/u/amit112amit)
#### Post date: [June 2, 2019, 2:27pm UTC](https://discourse.vtk.org/t/how-to-append-output-to-xdmf-file-in-a-time-series-simulation/1066/1 "2019-06-02T14:27:02Z")

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Hi.  
I noticed that `vtkXdmf3Writer` has `WriteAllTimeSteps` function. I have a simulation that updates a `vtkPolyData` as a function of time. But the program can run for several hours. So I want to keep writing out the `vtkPolyData` structure along with the corresponding simulation time periodically. To avoid generating several files, I am thinking of writing all the files to a XDMF file which will use HDF5 file to store the heavy data. But I am unable to understand how to do this.

1. How to associate a time stamp with a vtkPolyData?
2. How to append a new time stamp to an existing XDMF file?

Kindly let me know if this is possible with the existing VTK classes or if there is an example that I could follow.

Regards,  
Amit