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AWS Announced New Scaling and Availability Features for Oracle Databases

Amazon will soon release Multi-AZ deployments and Read Replicas for Oracle databases

Oracle database is offering a rich set of HA options in a non-Amazon world - active/passive clusters based on operating system failover capabilities (for example, IBM HACMP), active/active instances -  Oracle RAC (Real Application Clusters), Oracle Data Guard (physical and logical standby databases located in remote data center). Amazon Web Services RDS (Relational Database Service)  is already offering multi-AZ deployments for MySQL, soon to be released for Oracle databases too.

Multi-AZ deployment means that a simple click will suffice to create an Oracle physical standby database - an exercise which easily takes a day or two if done manually, even by an experienced DBA. Your primary database will thus be instantly protected by a robust standby database. When database is created or modified to run as a Multi-AZ deployment, Amazon RDS will automatically provision and manage physical standby database in a different Availability Zone. Availability Zone is independent infrastructure in a physically separate location. Standby database is not open for user community, the only function it performs is to apply archive log files from primary database. In case of primary database failure or planned outage standby database will automatically become active. It is still not clear if Amazon RDS will perform failover ( an Oracle term meaning physical standby database becomes active, while primary database is trashed and must be rebuilt ), or switchover ( physical standby database becomes active, while primary database now takes standby role ). We think Amazon RDS will probably take failover route.

Read Replica is an AWS feature that addresses one of notoriously difficult problems in RDBMS world - horizontal scaling. Relational databases are roughly classified as either OLTP or OLAP databases i.e. transactional (mostly data updates, i.e., INSERTS, UPDATES or DELETES) or analytical (mostly SELECT, i.e., read activity ). In order to avoid performance problems long running queries are usually not allowed to run on OLTP databases. OLAP databases containing aggregated data or copies of OLTP databases are created for query purposes. Techniques used in non-Amazon world are either custom scripted batch jobs that feed data from OLTP databases, split mirror techniques to quickly produce source database copy ( very useful for Very Large Databases ), logical standby databases etc.

While it is not currently known which of these techniques Amazon RDS will use as foundation of Read Replica feature for Oracle databases, we think that Oracle Active Data Guard feature will be used for this purpose. This feature allows for read-only access to physical standby database for queries while archive logs from primary database are continuously applied.

More Stories By Ranko Mosic

Ranko Mosic, BScEng, is specializing in Big Data/Data Architecture consulting services ( database/data architecture, machine learning ). His clients are in finance, retail, telecommunications industries. Ranko is welcoming inquiries about his availability for consulting engagements and can be reached at 408-757-0053 or ranko.mosic@gmail.com