SAMPLE - 1
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 were 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 few
rollback data. The delete command, on the other hand, is a DML operation, which
will produce rollback data 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 some examples of the types of database contraints you may find in
Oracle and indicate their purpose.
A Primary or Unique Key can be used to enforce uniqueness
on one or more columns.
A Referential Integrity Contraint can be used to enforce
a Foreign Key relationship between two tables.
A Not Null constraint - to ensure a value is entered in a
column
A Value Constraint - to check a column value against a
specific set of values.
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.
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