I've been asked the following Question in a 'Skill a Test' Exam
Could I get the corect answer with clarification?
In the event of data loss, what recovery method is required?
A: data import
B: media recovery
C: database recovery
D: point in time recovery
The correct answer to the question is point in time recovery.In point in time recovery u bring ur database to the point when it crashed so there is no data loss and is called a complete recovery.
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Rohit Nirkhe,Oracle DBA,OCP 8i
Thanks a lot for ur prompt reply.
Hi, 9th April 2001 15:39 hrs chennai
1)Your query miss some more valid points.For eg.Whether he has quoted
ARCHIVE Mode or NOARCHIVE Mode.
2)If it is in NOARCHIVE mode you cannot do point in time recovery.(or media recovery) only whole DB recovery can be done.
3)Going by the default mode (NOARCHIVE) if he has not mentioned the mode then you can do data import to recover the lost data(That too if the last data has a valid latest export data).Data import can be done in both modes.
4)So its ideal you have chosen the data import.
I agree with Data Import (A). If you protect critical data using export, then losing that DATA, through dropping tables, deleting rows or invalid updates, you can recover lost data by importing that table from your prior export. The other options don't necessarily involve data loss at all.
I don't like this kind of multi choose exam because all answer
are depends on the environment and what failure. For instance,
if noarchive, how you do point in time recovery?
if media failure, 1. if you lose all redo files? 2. what if you lose control file, 3. what if you lose whoe database ....
each one make you using different recovery method and
sometime do incomplete recovery and sometimes complete recovery.
so which one is the answer, all or none?
my answer is whoever make this exam should take an exam to qualify "exam" other people.
There is only one correct answer. data import is the only solution which applies ONLY to data loss. The others could apply depending upon circumstances. Thus this question does test your knowledge. That's the point of testing - evaluate those fine gradations of knowledge. Do you know what's appropriate for data loss?
let us say, daily backup plus import/export done 8AM,
1) 10AM user delete a table by mistake. import/export only can recover to 8am, so you are doing data incomplete recovery.
2) 10AM the whole "data" disk pack gone, you can use either
import/export or media recovery or ..
3) 10AM data plus all control files gone, import/export not work, you have to...
so which one is the answer??? if import/exprot can take care
every data failure, why we need other backup method.
if the question is how to recovery data loss if the database is up running noramlly, I agree the answer is import/export.
"That's the point of testing - evaluate those fine gradations of knowledge."
- the point of testee is to learn those fuzzy questions-answers before test.
One rule of thumb: answer C(out of a,b,c,d) can be is very often(because it is not last or first and one usually reads from top to bottom thus vasting precious time)