In Denodo, ‘**Too many open files**’ error occurs when you are executing costly operations with large views that use swapping mechanism and the swapping has exceeded the maximum number of open files allowed by your operating system.
You could avoid this error by reducing the number of files created by the swapping mechanism by modifying the Memory Usage settings of the Virtual DataPortserver. To achieve this, you could perform the following steps:
1. Navigate to "Administration > Server configuration > Memory usage" in the Web Design Studio.
* Increase the value of "Maximum size in memory of each node" parameter.
* You could also increase the "Maximum size of blocks stored in swap" parameter to create larger files. By creating files of larger size you can reduce the number of files created and thereby prevent the error.
2. Increase the maximum number of open files allowed by your Linux operating system. You can take a look at the [Linux Installation](https://community.denodo.com/kb/en/view/document/Denodo%20Admin%20and%20Development%20Best%20Practices#h.m4hlbwqltlfy-1:~:text=or%20data%20files.-,Linux%20Installation,-The%20recommended%20folder) section of the Denodo Admin and Development Best Practices Knowledge Base article.
You could take a look at the [**Configuring the Memory Usage and Swapping Policy**](https://community.denodo.com/docs/html/browse/latest/en/vdp/administration/server_configuration/configuring_the_memory_usage_and_swapping_policy/configuring_the_memory_usage_and_swapping_policy) section of the Virtual DataPort Administration Guide for more information on Memory usage settings.
If the issue persists and if you are a valid support user, you could create a support case on Denodo Support Site so that our team will assist you.
Hope this helps!