This video provides information on how to make sure that file descriptors are set to the recommended value and also to debug in case the file descriptors are set to a value lower than the recommended value.
How to automate the repository and domain back up process for disaster recovery in PowerCenter
How to unassign services from an expired key and assign them to a valid key in 9.1.0 and 9.5.1
How to find in which host the Repository Integration service is running in a multi node domain