Altair® Panopticon


Managing File Handles

In some cases, the Tomcat process that runs the Panopticon server may run out of file descriptors, which are handles used by the operating system to access a file (file handles). Panopticon data connections and license units checkouts count towards the total number of file handles in use.

When the maximum limit of file handles (open files) is reached, you cannot open any additional files, or make any additional TCP connections, or check out additional Altair license units.

On a Linux system, maximum file handles limit (open files) and other limits such as memory usage are called Resource Limits or rlimits. The rlimit values can be viewed and changed using the ulimit command and various arguments to that command. Please refer to Linux documentation for details on using the ulimit command, for example

The system will have an overall limit (global system maximum) as set in the kernel variable file /proc/sys/fs/file-max. In addition, there are rlimits set for each process, or for each user running a process. The rlimits for any given process will have a soft limit and a hard limit. The soft limit is what will be in effect, and the hard limit says what the maximum is if you want to raise the soft limit.

The reason for setting rlimits specific for a process that are lower than the overall system rlimits, is that you want to economize system resources between several processes to ensure that no single process consumes all available system resources, thereby causing problems for other processes. Likewise, a process specific rlimit set lower than the system maximum is also useful for protecting the system, avoiding system total resource depletion.