I didn't mean to demoralize you but if you read the manual two years
ago, you need to re-read it. And I do suggest that you play with things
in Oracle and read the manuals to understand what is going on.
I still think you need to do research to get the answers to your
questions but here are some of the answers. And you HAVE to read, we
can't teach you everything you would need to know:
- username and password can be found in the dba_users view. The
password is stored encrypted and cannot be manually verified. Error
messages displayed by the database processes are stored in the files in
the ORACLE_HOME/rdbms/mesg directory
- The question is misleading as extents are not automatically
allocated to a user when they are assigned to a tablespace. When the
users who have that tablespace as their temporary tablespace need temp
segments, the allocation of extents will be based on the default
storage parameters of the tablespace. If they wanted to know the
maximum space a user could use in that tablespace, you would need to
know the quota that was assigned to them -- in dba_ts_quotas.
- Redo logs and rollback segments serve two different purposes.
rollback segments are used within the database, to provide a consistent
picture of a changing table to other users or to allow the user making
changes to "rollback" their changes from the database. Redo logs are
used when the database needs to do recovery. Oracle does NOT read the
redo logs while the database is up and open, it only writes to them.
- of course the rollback segment has something to do with inserts and
imports.... as long as you are not doing them in nologging mode (even
then, the rbs is written to for system metadata). The only time you
don't write to a rollback segment is when you are doing a select -- and
you might need to read them at that point.
Rollback segments don't have autoextend -- I presume you mean the
tablespace datafiles do not have autoextend. If you cannot get enough
rollback space for the entire insert/import, and you are not doing an
interim commit, you will lose the transaction and the changes you have
made so far will be removed from the database when you fail to extend
the rollback segment. If you have interim commits, you will a) need
less rollback space and b) retain the data that has been committed.
5) deferred rollback segments are used for transactions in tablespaces
that were taken offline while the transaction was in flight.
6) You cannot change the ownership of the process to the user who
logged into the database because the user is not actually in the
database, but is interfacing with an executing shared program which is
owned by Oracle and therefore the process in the database is owned by
oracle.
7) infrequent commits in a long-running transaction can be the cause of
an 0ra-1555. Most of the time the problem is not that the rollback
segment is too small. You can also have too few rollback segments. In
general though, the problem is in the way the application(s) are coded
and not within the database.
8) the tables are in both memory and the datafiles.
9) freelists are stored in the segment data block headers, NOT in the
datafile headers
- Dharani Ravi <dharan71_at_yahoo.com> wrote:
> Dear Rachel,
>
> Thanks for your reply. Initially I felt demoralised
> after reading your reply. Truth is always bitter.
> You are correct. My Oracle concepts knowledge needs
> to be improved. I read Oracle 8 concepts manual two
> years ago. I am working for a small company where
> there are no seperate DBAs, System Administrators and
> Network Admins. Only three staff are identified to
> look after the abovementioned jobs in addition to
> development job. Most of our time goes for report
> generation, foxpro programs and other activities. I
> do not have a senior person from whom I can learn the
> job. Jobs like DB creation, maintanence, backup and
> recovery are done by me and I learned the job from
> manuals and by experience. I wanted to work in a
> production env where I can learn more about DBA job.
> I need your guidance and seniors guidance from this
> group. Hope you will appreciate my position and I
> sincerely request you to clarify my doubts. I will be
> grateful to you If you can clarify my mistakes made by
> me in the interview. I seek the support from this
> group to develop myself as a DBA.
>
> Merry Christmas.
>
> Regards.
> Dharan.
> --- Rachel Carmichael <wisernet100_at_yahoo.com> wrote:
> > Dharan,
> >
> > Answering just those questions will not give you
> > enough knowledge to
> > truly be able to answer Oracle questions in an
> > interview.
> >
> > Based on the answers you gave, it seems to me that
> > you do not
> > understand the concepts behind how Oracle works at
> > all. I would
> > suggest you read the documentation (specifically the
> > Concepts and
> > Administrator's manuals to start) to get a better
> > understanding of
> > Oracle.
> >
> > I would also suggest you talk to the senior DBA
> > where you are and ask
> > him or her to help you learn about the database.
> >
> > Rachel
> >
> > --- Dharani Ravi <dharan71_at_yahoo.com> wrote:
> > > Dear Seniors,
> > >
> > > I am a junior DBA and last weekend I attended a
> > > interview for DBA post. The following questions
> > were
> > > asked to me and I could not able to answer to the
> > > employers satsifaction. He asked me around 20
> > > questions and the following are the questions
> > where I
> > > have not fared well. Could Seniors help me by
> > giving
> > > the appropriate answers for the following
> > questions :
> > >
> > > 1) When you enter 'sqlplus scott/tiger' which
> > > background process checks for authentication ?
> > From
> > > which table/view it checks for authentication ?
> > If
> > > password is wrong from where oracle throws the msg
> > ?
> > > (I told server process, but could not remember the
> > > dictionary file and error msg file)
> > >
> > > 2) If you create a permanent tablespace and allot
> > it
> > > to 5 users as temporary tablespace, how many
> > extents
> > > will be allocated by oracle for each user ? (I
> > > answered that initial and next extent values will
> > be
> > > alloted to the user. The employer told that my
> > answer
> > > is not upto the mark)
> > >
> > > 3) When redo log contains both roll forward and
> > > rollback entries, why you require a separate
> > rollback
> > > segment ? (I told that redo files are fixed in
> > size
> > > and will be overwritten for large transaction,
> > whereas
> > > rbs will grow to accommodate the entire
> > transaction if
> > > autoextend is on and space is available)
> > >
> > > 4) When you insert or import 8 GB of data and
> > your
> > > rollback segment is of 100 MB size (without
> > > autoextend), then what will happen to the
> > transaction
> > > ? During inserts or import what entries will goto
> > > rollback segment ? (I told rbs has nothing to do
> > with
> > > insert or import)
> > >
> > > 5) When deferred rollback segment is used ? ( I
> > could
> > > not able to answer this question)
> > >
> > > 6) Is it possible to change ownership of Process
> > IDs
> > > from oracle to the user who have invoked the
> > process
> > > (for example all scott user processes are owned by
> > > Oracle user when you check in unix ps -ef |grep
> > oracle
> > > command). Why the PIDs are owned by Oracle
> > instead of
> > > the user who has invoked it ? (I answered -
> > because
> > > the listener starts the process, the ownership is
> > > showing as oralce instead of the actual user. I
> > could
> > > not able to answer how to change the ownership)
> > >
> > > 7) What are the other reasons for ORA-1555 error
> > > except rbs size is small ?
> > >
> > > 8) After starting database, where will the
> > dictionary
> > > files will reside (memory or system tablespace
> > > datafile). If your answer is memory, then whether
> > all
> > > the v$ and x$ and other dictionary files are
> > loaded in
> > > memory ? ( I answered that it depeneds upon the
> > size
> > > of SGA).
> > >
> > >
> > > 9) Where freelists are stored ? (I told that it
> > is
> > > stored in datafile header)
> > >
> > > 10) Is 'direct_io' parameter is equal to raw
> > device
> > > (I answered that to some extent it is true).
> > >
> > > Thanks in advance.
> > > Dharan.
> > >
> > >
> > > __________________________________________________
> > > Do You Yahoo!?
> > > Send your FREE holiday greetings online!
> > > http://greetings.yahoo.com
> > > --
> > > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.com
> > > --
> > > Author: Dharani Ravi
> > > INET: dharan71_at_yahoo.com
> > >
> > > Fat City Network Services -- (858) 538-5051
> > FAX: (858) 538-5051
> > > San Diego, California -- Public Internet
> > access / Mailing
> > > Lists
> > >
> >
> --------------------------------------------------------------------
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> >
> > __________________________________________________
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> > Send your FREE holiday greetings online!
> > http://greetings.yahoo.com
> > --
> > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.com
> > --
> > Author: Rachel Carmichael
> > INET: wisernet100_at_yahoo.com
> >
> > Fat City Network Services -- (858) 538-5051 FAX:
> > (858) 538-5051
> > San Diego, California -- Public Internet
>
=== message truncated ===
Do You Yahoo!?
Send your FREE holiday greetings online!
http://greetings.yahoo.com
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Rachel Carmichael
INET: wisernet100_at_yahoo.com
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
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Received on Tue Dec 25 2001 - 11:03:29 CST
