In addition to supporting BS2000 standard procedures, UDS/SQL also offers certain independent functions which ensure data security and availability in the event of failure of individual resources.
To meet high availability demands, the RLOG files in UDS/SQL which contain the before and after images of each modification, and which are used for a warm start of the database after a failure, can also be duplicated. This form of redundant data storage offers an alternative to RAID technology or to DRV. If RLOG files are duplicated, UDS/SQL automatically checks, where possible, whether two independent volumes have been specified for the RLOG files; if not, the RLOG files will not be created.
Reserve volumes can be specified for storing RLOG and ALOG files, and then be used when the original volumes fail. This can greatly reduce downtime resulting from the failure of logging volumes. You can manage reserve volumes with the DBH load parameter PP RESERVE, the DAL command MODIFY RESERVE and the BMEND statement START-LOG. When the availability of currently assigned logging files is impacted, the DBH automatically switches to the assigned reserve volumes.
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