Session

Programs use sessions to insulate data grid operations within program threads and to unite operations within transactions.

An application program usually creates only one connection to a data grid. From that connection object, a program can create one or many session objects.

Session objects are lightweight.

Sessions and Threads

It is good practice to create a separate session for each program thread that accesses the data grid.

Programs must use sessions in a thread-safe way. That is, two threads must not simultaneously access the same session. Violating this constraint can yield unpredictable results.

Sessions and Transactions

Each session can be either transacted or non-transacted. Programs determine this semantic property when creating each session.

In a transacted session, all get, put, and delete operations occur within a transaction, which is bound to the session. The session implicitly starts the transaction. Programs explicitly call the session's commit and rollback methods. (As these methods complete, they automatically start a new transaction in the session.)

If a program operates within several open transactions simultaneously, use a separate session and thread for each transaction.

In a non-transacted session, put, get, and delete operations are immediate: that is, when the method completes, the effect of the operation is also complete.

However, operations in a transacted session can block operations in a non-transacted session. For further explanation, see Transaction Isolation.

Only get, put, and delete operations are affected by a transacted session, the corresponding commit, and rollback APIs. Other commands such as iterators, queries, DDL updates, and so on do not have different behavior when running on a transacted session versus a non-transacted session.

Sessions and Defining Tables

Once a session has been created, it can be used to define tables programmatically. For more information, see "Defining a Table Using SQL DDL Commands" in the TIBCO ActiveSpaces Administration guide.