Framework/application to have inmemory copy of DataBase data

We have a requirement to have a In Memory copy of data from our different Relational DB servers.

Also keep the memory image updated if data in Relatio开发者_开发百科nal DB servers is changing.

is there any framework/application we can utilize to serve this requirement.

To have something in memory is not requirement, requirement is a reson for that - what is the reason ? ORMs (Hibernate, EclipseLink etc.) usually do some caching, if it's not enough, try some caches (EHcache, JBoss Cache, ...) and set some cache loaders for them (look at Apple's EOM for inspiration, it's quite simple).