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OrclDB_Replicatiion.

I want to clarify something on replication.

When is it actually needed?

If we want a cold DR site for our production database or even hot, do we really need replication?

my understanding this is needed for real-time failover or DR site only and that oracle uses Data guard for it.

however, i beleive we can always restore from nightly backups for last night snapshot or apply redo logs to get point in time recovery.

can you explain/cnfirm?
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sam15
Asked:
sam15
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2 Solutions
 
sdstuberCommented:
>>>I beleive we can always restore from nightly backups for last night snapshot or apply redo logs to get point in time recovery.

you are correct,  if you don't need a live standby then a backup with redo logs is sufficient for point in time recovery
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schwertnerCommented:
I do not know what DR is.

The problem you explain has some difficulties.

The main problem will be where you store the backups and the archive logs.

In all cases you have to keep them far away from the Productive Server. This is so because in the case of the disks failure, fire, earthquake (I believe this will not happen to you!) the archive backup files will get lost. So you can avoid Data Guard, but keep the recovery files far away from the productive DB.

Data Guard is an good way to have spare DB replica but it needs hardware resources and maintanance.
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sdstuberCommented:
DR - stands for Disaster Recovery
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slightwv (䄆 Netminder) Commented:
>>i beleive we can always restore from nightly backups for last night snapshot or apply redo logs to get point in time recovery.

Say you take backups nightly at 10:00 PM.

Your server dies, and by die I mean catches fire and melts, at 7:00 PM.

What is your possible recovery point?

You don't necessarily need Data Guard.  There are other options.  I currently use Oracle Streams replication and am very happy with it.  I've been told that the new Active Data Guard is built on top of Streams Replication.

There is also the newer GoldenGate product.
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sam15Author Commented:
but why do you need dataguard, streams, or goldengate to do replication?

is it only when you need a *LIVE* or *REAL-TIME* 2nd production server in case the first one dies.

I assume the only advantage with replication here is there is ZERO downtime but when use the restore from backup method (whenever disaster strikes) there is time delay in getting another production built. correct?

My requirement is cold backups. I have 3 days to get server back up if something happens. I beleive i do not need to get intop repication adn the complexity of installing it, maintaining it ,etc. correct?
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slightwv (䄆 Netminder) Commented:
>>is it only when you need a *LIVE* or *REAL-TIME*

sort of.  Data Guard can be passive and need manual intervention for failover.

>>there is ZERO downtime

It depends on how everything is set up.

>>My requirement is cold backups.

This is technically not replication.

>>the complexity of installing it, maintaining it ,etc. correct?
>>I have 3 days to get server back up if something happens

How much data can you lose?

re: the question I asked above:
Say you take backups nightly at 10:00 PM.

Your server dies, and by die I mean catches fire and melts, at 7:00 PM.

What is your possible recovery point?
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sdstuberCommented:
it's not so much the schedule of backups, but the schedule of the copy of backup and logs (probably different schedules)

frequent backups and copy will ensure more rapid restoration (fewer logs to apply)

frequent log copy will lessen data loss.
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sam15Author Commented:
<<How much data can you lose?>>

1 day is accetable. If i can get database back to time it crashes it would be better too (if possible).
It is not mandatory.

I am trying to see when you really need to implement replication? What kind of requiement I tell you that requires you to say you must have replication.? Is it also complex to setup. maintain or not?

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slightwv (䄆 Netminder) Commented:
>>What kind of requiement I tell you that requires you to say you must have replication.?

Main reason, two Words:  High Availibility.

replication isn't the only way to achieve this.

Another reason for replication is moving the data closer to the user.  You can replicate data across regional servers so regional users get quicker access.

>>Is it also complex to setup. maintain or not?

It depends on what method you use.

Streams replication is pretty complex to learn from scratch because there isn't a lot of information on it aside from the online docs.

Once you learn it, like anything else, it isn't hard to maintain.

Data Guard seems to be pretty straight forward but I've never set it up.
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sdstuberCommented:
no, you do not need replication.

especially with a one day of acceptable data loss.

take a daily backup and copy that backup to safe remote area
copy logs every 15 minutes.  You'll never lose more than 15 minutes of data
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sam15Author Commented:
Great solution.

When you say take a daily backup and copy it to safe remote area, do you mean taking an RMAN physical backup and copying to a different disk or some other disk outside of the building where prod server is located at.

I assume the DB backup and redolog copy can be automated using OEM and i dont have to do it manually myself. right?
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sdstuberCommented:
yes  and yes.

RMAN can do all of that for you and you can manage it through OEM.
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sam15Author Commented:
RMAN is only for oracle files but also cant you do take a mirror image of your production box using something like acronis

http://www.acronis.com/

And rebuild your DR machine exactly like prod server that went down.

I assume you dont need to do that since the O/S , oracle server and other programs are already installed on the DR machine and all you need is create a database and restore from backup.
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slightwv (䄆 Netminder) Commented:
Not familiar with acronis but if you shut down Oracle first or set up Oracle VSS (Volume Shadow Copy) you should be OK.

You cannot just copy open database files.
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sdstuberCommented:
I don't use acronis,


but your assumption is correct.  if rapid failover isn't a requirement, then yes, I go with simple recovery of backup
with oracle already installed on the box.

I see a few weeks ago you asked about using a dev box to recover production.

If you're asking about the same scenario, then I stand by going with simple recovery of backup.
Since it's a dev machine, you'll already have oracle installed.  

All you need to do is the recovery, possibly moving datafiles around if your filesystems are different and you're ready to go.
You wouldn't want replication or any other live-synching to production.
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