Disaster recovery strategies require a means to quickly relocate processing to a site in a different geographic location to the primary processing center.
A hot standby server is an ideal solution for remote database mirroring, or Remote Database Backup (RDB), as it is sometimes called.
Without SDS, you can achieve a remote database backup by using ‘volume level’ hardware or software mirroring. These solutions are typically expensive to implement, in particular, to achieve acceptable performance very high‑speed networks are essential.
SDS provides a cost-effective alternative that also supports read-only access on secondary databases. (Read-only access to a volume-replicated database is not viable using third-party mirroring solutions because of cache and disk image consistency issues.)
When a primary database or an offline copy of a primary database is opened, the current write journal (that is, the write journal that was open when the database was last closed) is mandatory.