Hi Ari,
     I am working as Oracle 7.x DBA on HP-UX 10.x Platform. I need Several
Clarifications, I visited your Site and It was very much relavent and helpful, I
felt you can clarify them. Thank you in advance. My email id's are 
bhas43@hotmail.com or bhas_m@yahoo.com.

1) What are the advantages of using Multi threaded Server Configuration?
   How do you avoid Network Traffic (between Remote Servers) in this case?

MTS allows for pooling of connections. So, if your server can only handle
1000 processes and your database is expected 2000 concurrent users, you
would need to use MTS. Each spawned listener process can handle transactions
from multiple connections. It is counted as "one" server process.

2) Is it possible to start multiple listener process concurrently? If yes how?

Not that I have ever done. Theoretically you can start different listeners
on different ports only if you have different ORACLE_HOMEs set. Don't know why
you would want to do this, though.

3) In order to enable Parallel Query Option, What are the minimum requirements?
   atleast Which are the parameters to be set in init.ora parameter file or
   is default option?

It depends on what you purchased. In Oracle8 it is a default option but with
Oracle7 it is an additional purchase. I don't have a manual here but there are
some init.ora parameters for the degree of parallel queries. You can also set
this at the table level and the query level. Check the manual for more on this.

4) I have set DB_WRITERS=6 and Number of hard disks in our Server is 3 for 
   Production Database. Some times what is happening that if you insert few 
   records and commit them, Same can be queried by other user after few minutes 
   and some of them will be missing. Can you explain why it happens so? Is it 
   because of DB_WRITERS parameter value?

This does not seem to make sense. If you commit a record, ALL users should
instantly be able to see the inserted records. If you can duplicate this for
Oracle support they would be grateful, since it shows that Oracle has a major
problem with it. It could be due to a DB_WRITER problem but if so it is a bug.

5) What are main differences between Oracle 7.x and 8 Versions?

I wrote a chapter on this in "Special Edition: Using Oracle8" by Que. Some main
differences are the Object-relational features (nested tables, VARRAY, TYPE
definitions), updateable views, improved password management, Net8 vs. SQL*Net,
and bit-mapped indexes all come to mind.

6) Whenever we add new Object/User to the database,  How Data Dictionary will be
   reflected?

The data dictionary is changed for all related tables and views. To go through
them all would take a lot of research on my behalf, but views like DBA_USERS,
DBA_TABLES, USER_TABLES, ALL_TABLES, ALL_TAB_COLUMNS, will be updated with
the new table or user information.

7) Sometimes When more number of users logs in to the System, Oracle will be
    automatically shutdown by saying "PMON process killed". why is it so?

It should not kill the PMON process. This sounds like a bug. Forward all
trace files (in ./bdump, ./cdump, and ./udump) with the alert.log to Oracle
Support.

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