User guide

Chapter 4 - Selecting Server Machines
Redundant License Servers
42 FLEXnet Licensing End User Guide
The user in Chicago could set LM_LICENSE_FILE to:
1700@chicago:1700@tokyo
The user in Tokyo could set LM_LICENSE_FILE to:
1700@tokyo:1700@chicago
Remember to separate the license file names with a colon (“ : ”) on UNIX and with a semicolon
(“ ; ”) on Windows. The application attempts the first server in the list, and if that fails for any
reason, the second server is tried.
Three-Server Redundancy
These three-server redundant servers need to have excellent communications on a reliable
network and need to be located on the same subnet. The three servers must be located physically
close to each other. This form of redundancy requires that the servers exchange heartbeats
periodically, and poor communications can cause poor performance. Avoid configuring
redundant servers with slow communications or dial-up links.
Three-server redundancy is designed to provide hardware failover protection only and does not
provide load-balancing. Use
LM_LICENSE_FILE list, instead, if load-balancing is desired. This
is because with three-server redundancy, only one of the three servers is “master,” capable of
issuing licenses. Since all clients must contact the “master,” all clients must have reliable
networking to a single machine.
Comparing Three-Server to License-File List
Are there any drawbacks to using the license-file list for redundancy?
Yes. By default, once a license job has successfully checked out a license from one host, all
subsequent checkouts must be satisfied from the same host. If the application requires more
than one license, this could result in a license denial when the license is available on another
server. An application bypasses this restriction if it is coded with the use of multiple FLEXnet
license jobs. Only your application vendor knows if their application is programmed in this
manner.
If the application supports license queueing, all licenses are queued only from the first host on
the list rather than the request moving to another server on the list.
Finally, if one server becomes unavailable, some licenses are unavailable.
When is it recommended to use a license-file list for redundancy rather
than three-server redundant servers?
• When there’s less system administration available to monitor license servers.
• When load-balancing is needed for FLEXenabled applications located far apart, e.g.,
London and Tokyo, make servers available locally, with remote servers available as
backup.
• License-file list is more forgiving if you lose quorum.