ACID-Compliant Databases

Cooperation occurs between the application server and the database server to ensure that transactions have basic properties that are referred to by the mnemonic ACID (see Table 16.1).

Table 16.1. Basic Database Properties Referred to by the Mnemonic ACID

Property	Description
Atomicity	Actions complete as a group or not at all.
Consistency	The state of the data storage remains consistent with the state of the business logic, whether the transaction succeeds or fails.
Isolation	Actions must run the same as if they were run serially .
Durability	Results of transactions must be stored persistently.

The database that you use with WebLogic Server must be ACID-compliant. The JDBC drivers offered by BEA WebLogic all connect to ACID-compliant databases.

Note

Any database used with an enterprise application must be ACID-compliant. For example, the MySQL database server added ACID compliance in September 2002 to enable development of e-commerce solutions to use MySQL. Prior to this release, MySQL could not be used with enterprise applications that required distributed transactions. Refer to the documentation provided by the database vendor for verification.

Whether the transaction is simple or distributed, the requirement is the same ”to complete a set of database actions as a group, which is referred to as atomicity (refer to Table 16.1). To support transaction management, the database being used must be ACID-compliant. An ACID-compliant database can process the standard SQL commands that are used with transaction management; these commands are shown in Table 16.2.

Table 16.2. Standard SQL Commands Used with Transaction Management

Command	Action
BEGIN or START	Signifies to the database that a transaction is being created. All subsequent database updates are within the scope of this transaction.
PREPARE	Signifies to the database that a distributed transaction is about to be committed. This command is not used with simple transactions.
COMMIT	Signifies to the database to write the transaction to persistent storage.
ROLLBACK	Signifies to the database that the current transaction must be discarded.