1. Explain the
difference between a hot backup and a cold backup and the benefits associated
A hot backup is basically taking a backup of
the database while it is still up and running and it must be in archive log
mode. A cold backup is taking a backup of the database while it is shut down
and does not require being in archive log mode. The benefit of taking a hot
backup is that the database is still available for use while the backup is
occurring and you can recover the database to any ball in time. The benefit of
taking a cold backup is that it is typically easier to administer the backup
and recovery process. In addition, since you are taking cold backups the
database does not require being in archive log mode and thus there will be a
slight performance gain as the database is not cutting archive logs to disk.
2. You have
just had to restore from backup and do not have any control files. How would
you go about bringing up this database?
I would create a text based backup control
file, stipulating where on disk all the data files where and then issue the
recover command with the using backup control file clause.
3. How do you
switch from an init.ora file to a spfile?
Issue the create spfile from pfile command.
4. Explain the
difference between a data block, an extent and a segment.
A data block is the smallest unit of logical
storage for a database object. As objects grow they take chunks of additional
storage that are composed of contiguous data blocks. These groupings of
contiguous data blocks are called extents. All the extents that an object
takes when grouped together are considered the segment of the database object.
5. Give two
examples of how you might determine the structure of the table DEPT.
Use the describe command or use the
6. Where would
you look for errors from the database engine?
In the alert log.
7. Compare and
contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command have the
desired outcome of getting rid of all the rows in a table. The difference
between the two is that the truncate command is a DDL operation and just moves
the high water mark and produces a now rollback. The delete command, on the
other hand, is a DML operation, which will produce a rollback and thus take
longer to complete.
8. Give the
reasoning behind using an index.
Faster access to data blocks in a table.
9. Give the
two types of tables involved in producing a star schema and the type of data
Fact tables and dimension tables. A fact table
contains measurements while dimension tables will contain data that will help
describe the fact tables.
10. . What type of index should you
use on a fact table?
A Bitmap index.
11. Give two examples of referential
A primary key and a foreign key.
12. A table is classified as a parent
table and you want to drop and re-create it. How would you do this without
affecting the children tables?
Disable the foreign key constraint to the
parent, drop the table, re-create the table, enable the foreign key
13. Explain the difference between
ARCHIVELOG mode and NOARCHIVELOG mode and the benefits and disadvantages to
ARCHIVELOG mode is a mode that you can put the
database in for creating a backup of all transactions that have occurred in
the database so that you can recover to any ball in time. NOARCHIVELOG mode is
basically the absence of ARCHIVELOG mode and has the disadvantage of not being
able to recover to any ball in time. NOARCHIVELOG mode does have the advantage
of not having to write transactions to an archive log and thus increases the
performance of the database slightly.
14. What command would you use to
create a backup control file?
Alter database backup control file to trace.
15. Give the stages of instance
startup to a usable state where normal users may access it.
STARTUP NOMOUNT - Instance startup
STARTUP MOUNT - The database is mounted
STARTUP OPEN - The database is opened
16. What column differentiates the V$
views to the GV$ views and how?
The INST_ID column which indicates the
instance in a RAC environment the information came from.
17. How would you go about generating
an EXPLAIN plan?
Create a plan table with utlxplan.sql.
Use the explain plan set statement_id = 'tst1'
into plan_table for a SQL statement
Look at the explain plan with utlxplp.sql or
18. How would you go about increasing
the buffer cache hit ratio?
Use the buffer cache advisory over a given
workload and then query the v$db_cache_advice table. If a change was necessary
then I would use the alter system set db_cache_size command.
19. Explain an ORA-01555
You get this error when you get a snapshot too
old within rollback. It can usually be solved by increasing the undo retention
or increasing the size of rollbacks. You should also look at the logic
involved in the application getting the error message.
20. Explain the difference between $ORACLE_HOME
ORACLE_BASE is the root directory for oracle.
ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.