Application caching is critical to running any large-scale web application. Understanding how application caching works and what some of the options you have to help your Blackboard Learn instance run efficiently, helps you make decisions about investing in hardware and software. If you are not familiar with the concept of caching, read Cache (computing) on Wikipedia.
Ehcache is an open source cache library that Blackboard Learn uses by default. Its configurations for the core caches are defined in your Blackboard Learn installation inside the config/cache-settings.properties file.
Beginning in 9.1 Service Pack 11, a new deployment configuration for leveraging advanced caching is available. The Redis Cache building block enables Blackboard Learn's cache framework to use Redis as an additional type of memory store outside the JVM heap. Redis is an open source, high-performance, networked advanced key-value store. Other companies that use Redis include Twitter, Craigslist, Github, Stackoverflow, and Instagram.