siva@bally.Bally.COM (Siva Chelliah/50000) (05/08/91)
Is there any database capable of updating a redundant database resides on a different machine? Our real time system requires a redundant computer running. So whenever the on-line system updates the database the off-line system also should update its database. Then if the on-line system crashes then the off-line system can become on-line. Any help will be appreciated. Thanks siva
dhepner@hpcuhc.cup.hp.com (Dan Hepner) (05/22/91)
From: siva@bally.Bally.COM (Siva Chelliah/50000) >Is there any database capable of updating a redundant database resides on a >different machine? >Our real time system requires a redundant computer running. So whenever the >on-line system updates the database the off-line system also should update >its database. Then if the on-line system crashes then the off-line system >can become on-line. > >Any help will be appreciated. >siva It should be possible "any time now" to write an application which can use redundant Informix databases, and using the Tuxedo/T TP Monitor, effect an atomic commit across both, with the application being responsible to react to failures of the redundant system. The most reasonable first target for discussion of availability would seem to be your hardware vendor, or Informix. This is not to claim that Informix is unique in this regard, but they do seem ahead of some of their competition. Some competitive offerings might be close to offering this functionality "internally", which was probably more what you had in mind. It might be worth pointing out that this solution occupies a slice of a spectrum of redundant solutions. Many concerns are addressed by mirrored disks, and thus a mirrored database, as supplied by both systems vendors as well as DBMS vendors. Several system vendors, including HP, offer "fail-over" capability, which can have a backup take over a database for a failed primary system, and bring up the application in a way which requires no special coding of the application. And of course there are fault tolerant system offerings which also allow for total redundancy while not putting special coding requirements upon the application designer. The tradeoffs, as you can see, involve the system cost, the level of redundancy, and how much the application programmer might need to be involved in handling the failure. Dan Hepner This is not a statement of the Hewlett Packard Company.