WHAT IS IT ?
The product is an Object Database Management System (ODBMS).
It is written entirely in Java and is intended to be used by applications written in Java ( requires JDK 1.3 ).
The product provides
- automatic movement of objects between primary and secondary storage, akin to a virtual memory system
- a transaction environment with ACID properties, as expected of a DBMS
- client / server support
- distributed database support
- garbage collection on the database
- a combined database server / web server to run Java servlets
It is not a Relational Database Management System (RDBMS). It does not define tables. An application does not make explicit database calls.
PRODUCT EDITIONSAs of release 2, the product is split into three editions.
- Personal - single user with local database
- Standard - multi-user; client /server; web server
- Professional - distributed databases
MODES OF OPERATIONSix modes of operation are supported:.
- Standalone - single user application with local database
- Fat client / thin server - database objects execute on the client
- Thin client / fat server - database objects execute on the server
- Applet - client runtime executes as an applet in a browser
- Web server - Java servlets execute in the database server
- Distributed databases - multiple servers; two phase commit
PHILOSOPHY
Object technology means: send a message to an object and it happens. Whether the object is currently in primary storage, or where the object is located on the network, should be a problem for runtime software, not for the application.
The need to explicitly read and write records, to transform records to objects, and to manage the deletion of dead records, is considered to be a hybrid technology: objects on the surface and old procedural programming underneath.
PERSISTENCE
Persistence is defined by reachability. A special object is the root of a tree of objects. If an object is reachable from the root, then it persists. To make an object persist, attach it to another persistent object or directly to the root object.
Garbage collection is the other side of persistence. If an object is not reachable from the root, then it is garbage collected.
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