• 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.
Durability means that after a transaction has been committed, the committed transaction must be guaranteed, even if a database failure occurs before the changed data are physically written to a disk.
ALTIBASE HDB provides durability with a combination of checkpointing and transaction logging.
ALTIBASE HDB adheres to WAL (write-ahead logging) protocol. Based on WAL protocol, before overwriting an object with "uncommitted" updates, ALTIBASE HDB writes the log records related to such updates to disk storage for UNDO operations. And similarly, before committing an update to a database object, it writes the log records related to such an update to the log on disk storage for REDO operations.
Durability & Performance
In ALTIBASE HDB transaction durability has a significant influence on the processing performance. Especially on the memory-based side of the database which can potentially exhibit performance up to 20 times faster than the disk-based side of the database, guaranteeing transaction durability has a much bigger impact on performance. This is due the fact that based on the WAL protocol, in order for a ALTIBASE HDB to provide complete transaction durability, it has to write logs for all database updates to a log file on disk therefore introducing additional disk I/O activity which can degrade the performance.