Global caches are defined for every instance in a cluster. For a global cache, the attributes like cache size, buffer pool setting, are sysconfigures table, and all instances in a cluster read from this entry to create the cache on their respective instances.
It is possible to change such attributes as cache size, buffer pool settings, of a global cache to be instance-specific. If a particular instance has local settings, the cache is created using them. If the instance has no local definition, it uses a global definition to create the cache. In other words, instances that have local definitions override the global definitions and settings.
You can increase the size of local and global caches
dynamically, but you cannot reduce them dynamically.
