# Mrview unable to open images: "Too many open files"

**URL:** https://community.mrtrix.org/t/mrview-unable-to-open-images-too-many-open-files/2550
**Category:** Wiki
**Tags:** mrview, troubleshooting
**Created:** [May 23, 2019, 5:17pm UTC](https://community.mrtrix.org/t/mrview-unable-to-open-images-too-many-open-files/2550 "2019-05-23T17:17:27Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![rsmith](https://community.mrtrix.org/user_avatar/community.mrtrix.org/rsmith/32/2672_2.png) [@rsmith](https://community.mrtrix.org/u/rsmith)
#### Post date: [May 23, 2019, 5:17pm UTC](https://community.mrtrix.org/t/mrview-unable-to-open-images-too-many-open-files/2550/1 "2019-05-23T17:17:27Z")

</div>

It is possible to encounter this error message particularly if trying to open a large number of DICOM images. In most cases, each slice in a DICOM series is stored in an individual file; all of these files must remain open while the image is loaded. In addition, the maximum number of files open at any time (imposed by the kernel, _not_ _MRtrix3_) may be relatively small (e.g. 256), such that very few subjects can be opened at once.

There are two ways to solve this issue:

- **Reduce the number of files opened concurrently** : By converting each series of interest to an alternative format (e.g. [MRtrix image formats](https://mrtrix.readthedocs.io/en/latest/getting_started/image_data.html#mrtrix-image-formats-mih-mif)) before opening them in `mrview`, the total number of files open at once will be drastically reduced.

- **Increase the limit on number of files opened** : If directly opening DICOM images without first converting them is more convenient, then it is possible to instead increase the kernel’s upper limit on the number of files that can remain open at once. The specific details on how this is done may vary between different OS’s / distributions, but here are a couple of suggestions to try: