Database Administrator's Guide

FILES <Number of Files>

The maximum number of files to be open at one time.

There is no effective limit to the number of files supported by the FairCom Server, except for any limits imposed by the operating system and available system memory.

Note: The number of file descriptors set by the FILES keyword may need to be considerably greater than the number of open data files. Each index, whether or not in a separate file, counts toward this total. For example, a host index file that supports three different keys (i.e., contains three separate index members) counts as three files toward the FILES total. In addition, each member of a superfile is counted toward the total set by the FILES keyword.

Unix/Linux Considerations

The Unix and Linux operating systems place a limit on the number of file descriptors that can be in use at one time. The number of file descriptors required by FairCom DB is determined as follows:

• Each open file consumes 1 file descriptor (this may be somewhat lower than the setting of the FILES keyword because individual superfile members and members of a host index do not consume file descriptors).
• Each TCP/IP socket consumes a file descriptor (this corresponds to the CONNECTIONS keyword).
• FairCom DB reserves a few file descriptors in addition to those used for data files, index files, and TCP/IP connections.

Based on the above considerations, the system should be configured to allow a number somewhat greater than the number of files + connections.

The file descriptor limit is typically set by the limit or ulimit command, which may require superuser access, or by the hard limit set in a system configuration file such as /etc/security/limits.conf on Linux. The specifics vary by system, so consult the documentation for your Unix or Linux system. (Unix and Linux define both hard limits and soft limits. A soft limit can be changed by a process at any time, but it cannot exceed the hard limit. The hard limit is of interest for this discussion.)

Note: When the file descriptor limit for FairCom Server (set by the operating system) is set too low, server startup fails with error 1005 (system-dependent initialization failed). A message is written to standard output indicating that system-dependent initialization failed and that details are in CTSTATUS.FCS.

Features for Handling File Descriptor Limits

Several features improve the ability of the system to handle situations concerning file descriptors:

• Improved file descriptor server startup messages
• Fail server startup if file descriptor limit can't be increased to required value
• Write message to standard output when file descriptor limit is too low
• New file descriptor limit compatibility keyword

See Also

MAX_FILES_PER_USER

COMPATIBILITY FILE_DESCRIPTOR_LIMIT