Adaptive Server introduces in-memory (IMDB) and relaxed-durability databases with version 15.5. See the Adaptive Server Enterprise In-Memory Database Users Guide.
In-memory databases reside entirely in cache and do not use disk storage for data or logs, and therefore do not require disk I/O. This results in potentially greater performance than a traditional disk-resident database (DRDB), amongst other advantages. Since an in-memory database exists only in cache, you cannot recover the database if the supporting host is shut down or the database fails.
With relaxed-durability databases, Adaptive Server extends the performance benefits of an in-memory database to disk-resident databases. Disk-resident databases perform writes to disk, and ensure that the transactional properties of atomicity, consistency, integrity, and durability, known as the ACID properties, are maintained. A traditional disk-resident database operates at full durability to guarantee transactional recovery from a server failure. Relaxed-durability databases trade the full durability of committed transactions for enhanced runtime performance for transactional workloads. A relaxed-durability database created with the no_recovery level is similar to an in-memory database: you cannot recover data or logs if the server terminates or is shut down. You can also create a relaxed-durability database with the at_shutdown level where transactions are written to disk if there is a proper shut down of the database.
