Oracle Data Guard

[Chassidy Rentz]

So, as far as hardware requirements go, do you have to have a server as big or bigger as the one that houses the primary to house the standby database?
Also, say I have 2 regional servers that serve as primaries themselves. Is it feasible to have those 2 "back each other up" as standby's, each one keeping a synchronized copy of the other one's database in the background to it's own primary one?

[Steven E. Protter]

You need an equal amount of disk space though not necessarily the same server type and resources.

If you want instant takover, you need a machine that can handle your normal production load at least for a while.

SEP

[Yogeeraj_1 · Accepted solution]

hi,

below a few clarifications about the Data Guard.

If you are trying to implement data guard. You will have to choose between the 4 modes to data guard:

a. Guaranteed: "when we cannot get the redo to the failover site when we commit -- STOP, FAIL, HALT". Two phase commit like protection. either both or neither are updated.

b. Instant: "when we cannot get the redo to the failover site when we commit -- don't stop, don't fail -- rather fall back into using archives, notify the DBA, make OEM flash red, get the problem fixed ASAP". when all things are working normally, standby is upto the second. when something breaks in the connectivity between the two -- SOUND THE ALARMS, but don't stop production

c. Rapid: Caution: running in rapid mode when the standby is unavailable -- is sort of like running with a failed mirror disk in mirrored pairs. You can still write to the disk but if the disk fails -- you no longer have a mirror do you. It is up to you whether you want to continue or you want to stop.

d. delayed

In general, data guard is providing two things:
a. extremely high levels of data assurance. If it was committed, we got it.

b. a failover site that can be failed over to AS SOON AS A standby site for it is constructed (makes no sense to fail over if your requirement is to have two copies AT ALL TIMES)


hope this helps too!

regards
Yogeeraj