HP NonStop Remote Database Facility (RDF)

HP NonStop Remote Database Facility (RDF)

HP NonStop RDF extends the NonStop server’s fault tolerance to disaster recovery.

Using the audit trail generated by NonStop TMF and operating-system level services, RDF instantly replicates audited database changes to identical target databases on one or more target systems.

Thus, in the event of a failure of a primary system, the application can be recovered to a backup system within minutes and with minimal data loss. RDF will back out any incomplete transactions on the target system when the target system takes over processing.

RDF can be configured to protect individual audited files or tables, the contents of one or more subvolumes, or entire disk volumes. It can replicate changes to one or more target systems.

Alternatively, it can replicate changes from many source databases to a single target database to provide a single backup for multiple production systems. RDF is useful for upgrading hardware and software with no application downtime. The backup system is taken offline and upgraded. Application processing is then redirected to the upgraded backup system, and the other system is upgraded. Though applications on the target system cannot open databases for write access that are being replicated by RDF, they can read the target databases. On the target system, other applications can be running, replicating their database changes to other target systems. If the backup system has to take over processing, the backup applications open the application databases for write access before continuing application processing. There is a small time latency between when transactions are executed on the source system and when they have been successfully replicated to the target system.

Thus, transactions in the replication pipeline may be lost due to a primary system failure. If this loss is unacceptable, RDF implements a Zero Lost Transaction (ZLT) feature. With ZLT, the audit trail disk mirrors are split; and one mirror is located up to 100 kilometers from the production system. No transaction completes until it has been successfully written to the remote mirror. The remote mirror is available to a backup system if the backup system needs to take over processing with no lost transactions.