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ORACLE Interview Questions and Answers
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(Continued from previous part...)
862. What is import/export and why does one need it? (for DBA
The Oracle export (EXP) and import (IMP) utilities are used to perform logical database backup and recovery. They are also used to move Oracle data from one machine, database or schema to another.
The imp/exp utilities use an Oracle proprietary binary file format and can thus only be used between Oracle databases. One cannot export data and expect to import it into a non-Oracle database. For more information on how to load and unload data from files, read the SQL*Loader FAQ.
The export/import utilities are also commonly used to perform the following tasks:
. Backup and recovery (small databases only)
. Reorganization of data/ Eliminate database fragmentation
. Detect database corruption. Ensure that all the data can be read.
. Transporting tablespaces between databases
. Etc.
863. what is a display item?
Display items are similar to text items but store only fetched or assigned values. Operators cannot navigate to a display item or edit the value it contains.
867. How does one use the import/export utilities? (for DBA
Look for the "imp" and "exp" executables in your $ORACLE_HOME/bin directory. One can run them interactively, using command line parameters, or using parameter files. Look at the imp/exp parameters before starting. These parameters can be listed by executing the following commands: "exp help=yes" or "imp help=yes".
The following examples demonstrate how the imp/exp utilities can be used:
exp scott/tiger file=emp.dmp log=emp.log tables=emp rows=yes indexes=no
exp scott/tiger file=emp.dmp tables=(emp,dept)
imp scott/tiger file=emp.dmp full=yes
imp scott/tiger file=emp.dmp fromuser=scott touser=scott tables=dept
exp userid=scott/tiger@orcl parfile=export.txt
... where export.txt contains:
BUFFER=100000
FILE=account.dmp
FULL=n
OWNER=scott
GRANTS=y
COMPRESS=y
NOTE: If you do not like command line utilities, you can import and export data with the "Schema Manager" GUI that ships with Oracle Enterprise Manager (OEM).
868. What are the types of visual attribute settings?
Custom Visual attributes
Default visual attributes
Named Visual attributes.
Window
869. Can one export a subset of a table? (for DBA
From Oracle8i one can use the QUERY= export parameter to selectively unload a subset of the data from a table. Look at this example:
exp scott/tiger tables=emp query=\"where deptno=10\"
870. What are the two ways to incorporate images into a oracle forms application?
Boilerplate Images
Image_items
871. Can one monitor how fast a table is imported? (for DBA
If you need to monitor how fast rows are imported from a running import job, try one of the following methods:
Method 1:
select substr(sql_text,instr(sql_text,'INTO "'),30) table_name,
rows_processed,
round((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60,1) minutes,
trunc(rows_processed/((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60)) rows_per_min
from sys.v_$sqlarea
where sql_text like 'INSERT %INTO "%'
and command_type = 2
and open_versions > 0;
For this to work one needs to be on Oracle 7.3 or higher (7.2 might also be OK). If the import has more
than one table, this statement will only show information about the current table being imported.
Contributed by Osvaldo Ancarola, Bs. As. Argentina.
Method 2:
Use the FEEDBACK=n import parameter. This command will tell IMP to display a dot for every N rows imported.
872. Can one import tables to a different tablespace? (for DBA
Oracle offers no parameter to specify a different tablespace to import data into. Objects will be re-created in the tablespace they were originally exported from. One can alter this behaviour by following one of these procedures:
Pre-create the table(s) in the correct tablespace:
. Import the dump file using the INDEXFILE= option
. Edit the indexfile. Remove remarks and specify the correct tablespaces.
. Run this indexfile against your database, this will create the required tables in the appropriate tablespaces
. Import the table(s) with the IGNORE=Y option.
Change the default tablespace for the user:
. Revoke the "UNLIMITED TABLESPACE" privilege from the user
. Revoke the user's quota from the tablespace from where the object was exported. This forces the
import utility to create tables in the user's default tablespace.
. Make the tablespace to which you want to import the default tablespace for the user
. Import the table
873. What do you mean by a block in forms4.0?
Block is a single mechanism for grouping related items into a functional unit for storing, displaying and manipulating records.
(Continued on next part...)
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