WebSphere eXtreme Scale Product Overview > Cache concepts
|
| |
Database integration
WebSphere eXtreme Scale is used to front a traditional database and eliminate read activity that is normally pushed to the database. A coherent cache can be used with an application directly or indirectly using an object relational mapper. The coherent cache can then offload the database or backend from reads. In a slightly more complex scenario, such as transactional access to a data set where only some of the data requires traditional persistence guarantees, filtering can be used to offload even write transactions.
You can configure eXtreme Scale to function as a highly flexible in-memory database processing space. However, eXtreme Scale is not an object relational mapper (ORM). It does not know where the data in eXtreme Scale came from. An application or an ORM can place data in an eXtreme Scale server. It is the responsibility of the source of the data to make sure that it stays consistent with the database where data originated. This means eXtreme Scale cannot invalidate data that is pulled from a database automatically. The application or mapper must provide this function and manage the data stored in eXtreme Scale.
Figure 1. ObjectGrid as a database buffer
Figure 2. ObjectGrid as a side cache
- Sparse and complete cache
WebSphere eXtreme Scale can be used as a sparse cache or a complete cache. A sparse cache only keeps a subset of the total data, while a complete cache keeps all of the data. and can be populated lazily, on-demand. Sparse caches are normally accessed using keys (instead of indexes or queries) since the data is only partially available. - Side cache and in-line cache
WebSphere eXtreme Scale is used to provide in-line caching for a database back-end or as a side cache for a database. In-line caching uses eXtreme Scale as the primary means for interacting with the data. When eXtreme Scale is used as a side cache, the back-end is used in conjunction with the eXtreme Scale. - Database synchronization techniques
When WebSphere eXtreme Scale is used as a cache, applications must be written to tolerate stale data if the database can be updated independently from an eXtreme Scale transaction.To serve as a synchronized in-memory database processing space, eXtreme Scale provides several ways of keeping the cache updated.