Fault Tolerance, License Grace, and Redundancy

Sybase products check out licenses on start-up, and perform periodic heartbeat checks to verify that licenses remain available. If a license is unavailable, the product determines whether it can be awarded a grace period.

The grace period starts from the time a license was last in use and persists for 30 days for server products and 15 days for tool products. At the end of the grace period, the product performs an orderly shutdown, if running, or fails to start up, unless the license (or a replacement license) becomes available, at which point the cycle continues with the heartbeat, noting the last use of the license.

This tolerance for temporary licensing failure is usually sufficient. However, in certain circumstances, you may choose to use “three-license-server redundancy.” For example:

A grace period is not provided for Sybase Floating License (FL) type licenses.
Standby copy systems rarely qualify for grace as they are unlikely to have been used within the last 30 days.
Company policy dictates the use of redundancy.

For three-server redundancy, use three machines that each:

Run the same version of the SySAM license server.
Have good intermachine communication.
Use a separate copy of the same license files.

A product that uses per-processor licensing checks out a license quantity equal to the number of processors it can use, or awards runtime grace if an insufficient quantity is available. If the number of processors is dynamically increased while the product is running and the product is unable to check out additional licenses, runtime grace is also awarded. If the additional licenses are not made available within the runtime grace period the product shuts down. Decreasing the number of processors that a product can use while it is running does not reduce the required license quantity. You must restart the product on the correct number of processors.