Transaction
A database transaction is a logical unit of work that comprises one or more SQL statements. A transaction begins with the first execution of an SQL statement by a user, and ends when it is committed or rolled back, either explicitly with a COMMIT or ROLLBACK statement or implicitly when a DDL statement is issued.
ACID
To maintain database integrity, a properly executed transaction must exhibit the four ACID properties: Atomicity, Consistency, Isolation, and Durability.
• Atomicity - Either all of the statements that constitute a transaction are completely executed, or none of them are. That is, the transaction cannot be partially successful.
• Consistency - A properly executed transaction does not break the consistency of the database.
• Isolation - When multiple transactions are underway at the same time, none of the transactions have access to the results of the other transactions.
• Durability - Once a transaction has been committed, the resultant changes are not lost regardless of the circumstances, such as system failure.
ALTIBASE HDB guarantees reliable transactional processing by implementing a database server that satisfies all ACID requirements.