1. Explain the difference
between a hot backup and a cold backup and the benefits associated with each.
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 point 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
dbms_metadata.get_ddl package.
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 they hold.
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 integrity constraints.
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 constraint.
13. Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode
and the benefits and disadvantages to each.
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 point in time. NOARCHIVELOG mode is
basically the absence of ARCHIVELOG mode and has the disadvantage of not being
able to recover to any point 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
utlxpls.sql
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 and $ORACLE_BASE.
ORACLE_BASE is the root directory for oracle.
ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.
21. How would you determine the
time zone under which a database was operating?
select DBTIMEZONE from dual;
22. Explain the use of setting
GLOBAL_NAMES equal to TRUE.
Setting GLOBAL_NAMES dictates how you might connect
to a database. This variable is either TRUE or FALSE and if it is set to TRUE
it enforces database links to have the same name as the remote database to
which they are linking.
23. What command would you use to
encrypt a PL/SQL application?
WRAP
24. Explain the difference
between a FUNCTION, PROCEDURE and PACKAGE.
A function and procedure are the same in that they
are intended to be a collection of PL/SQL code that carries a single task. While
a procedure does not have to return any values to the calling application, a
function will return a single value. A package on the other hand is a
collection of functions and procedures that are grouped together based on their
commonality to a business function or application.
25. Explain the use of table
functions.
Table functions are designed to return a set of
rows through PL/SQL logic but are intended to be used as a normal table or view
in a SQL statement. They are also used to pipeline information in an ETL
process.
26. Name three advisory
statistics you can collect.
Buffer Cache Advice, Segment Level Statistics,
& Timed Statistics
27. Where in the Oracle directory
tree structure are audit traces placed?
In unix $ORACLE_HOME/rdbms/audit, in Windows the
event viewer
28. Explain materialized views
and how they are used.
Materialized views are objects that are reduced
sets of information that have been summarized, grouped, or aggregated from base
tables. They are typically used in data warehouse or decision support systems.
29. When a user process fails,
what background process cleans up after it?
PMON
30. What background process
refreshes materialized views?
The Job Queue Processes.
31. How would you determine what
sessions are connected and what resources they are waiting for?
Use of V$SESSION and V$SESSION_WAIT
32. Describe what redo logs are.
Redo logs are logical and physical structures that
are designed to hold all the changes made to a database and are intended to aid
in the recovery of a database.
33. How would you force a log
switch?
ALTER SYSTEM SWITCH LOGFILE;
34. Give two methods you could
use to determine what DDL changes have been made.
You could use Logminer or Streams
35. What does coalescing a
tablespace do?
Coalescing is only valid for dictionary-managed
tablespaces and de-fragments space by combining neighboring free extents into
large single extents.
36. What is the difference
between a TEMPORARY tablespace and a PERMANENT tablespace?
A temporary tablespace is used for temporary
objects such as sort structures while permanent tablespaces are used to store
those objects meant to be used as the true objects of the database.
37. Name a tablespace
automatically created when you create a database.
The SYSTEM tablespace.
38. When creating a user, what
permissions must you grant to allow them to connect to the database?
Grant the CONNECT to the user.
39. How do you add a data file to
a tablespace?
ALTER TABLESPACE <tablespace_name> ADD
DATAFILE <datafile_name> SIZE <size>
40. How do you resize a data
file?
ALTER DATABASE DATAFILE <datafile_name>
RESIZE <new_size>;
41. What view would you use to look
at the size of a data file?
DBA_DATA_FILES
42. What view would you use to
determine free space in a tablespace?
DBA_FREE_SPACE
43. How would you determine who
has added a row to a table?
Turn on fine grain auditing for the table.
44. How can you rebuild an index?
ALTER INDEX <index_name> REBUILD;
45. Explain what partitioning is
and what its benefit is.
Partitioning is a method of taking large tables and
indexes and splitting them into smaller, more manageable pieces.
46. You have just compiled a
PL/SQL package but got errors, how would you view the errors?
SHOW ERRORS
47. How can you gather statistics
on a table?
The ANALYZE command.
48. How can you enable a trace
for a session?
Use the DBMS_SESSION.SET_SQL_TRACE or
Use ALTER SESSION SET SQL_TRACE = TRUE;
49. What is the difference
between the SQL*Loader and IMPORT utilities?
These two Oracle utilities are used for loading
data into the database. The difference is that the import utility relies on the
data being produced by another Oracle utility EXPORT while the SQL*Loader
utility allows data to be loaded that has been produced by other utilities from
different data sources just so long as it conforms to ASCII formatted or
delimited files.
50. Name two files used for network
connection to a database.
TNSNAMES.ORA and SQLNET.ORA
No comments:
Post a Comment