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Computer Interview Questions Answers

Oracle Interview Questions Answers

Question - 141 : - What is cluster key?

Answer - 141 : - The related columns of the tables in a cluster are called the cluster key.

Question - 142 : - What does COMMIT do ?

Answer - 142 : - COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible to other user sessions transactions that start only after transaction is committed.

Question - 143 : - How does one see the uptime for a database? (for DBA )

Answer - 143 : - Look at the following SQL query: SELECT to_char (startup_time,'DD-MON-YYYY HH24: MI: SS') "DB Startup Time" FROM sys.v_$instance; Marco Bergman provided the following alternative solution: SELECT to_char (logon_time,'Dy dd Mon HH24: MI: SS') "DB Startup Time" FROM sys.v_$session WHERE Sid=1 /* this is pmon */ / Users still running on Oracle 7 can try one of the following queries: Column STARTED format a18 head 'STARTUP TIME' Select C.INSTANCE, to_date (JUL.VALUE, 'J') || to_char (floor (SEC.VALUE/3600), '09') || ':' -- || Substr (to_char (mod (SEC.VALUE/60, 60), '09'), 2, 2) || Substr (to_char (floor (mod (SEC.VALUE/60, 60)), '09'), 2, 2) || '.' || Substr (to_char (mod (SEC.VALUE, 60), '09'), 2, 2) STARTED from SYS.V_$INSTANCE JUL, SYS.V_$INSTANCE SEC, SYS.V_$THREAD C Where JUL.KEY like '%JULIAN%' and SEC.KEY like '%SECOND%'; Select to_date (JUL.VALUE, 'J') || to_char (to_date (SEC.VALUE, 'SSSSS'), ' HH24:MI:SS') STARTED from SYS.V_$INSTANCE JUL, SYS.V_$INSTANCE SEC where JUL.KEY like '%JULIAN%' and SEC.KEY like '%SECOND%'; select to_char (to_date (JUL.VALUE, 'J') + (SEC.VALUE/86400), -Return a DATE 'DD-MON-YY HH24:MI:SS') STARTED from V$INSTANCE JUL, V$INSTANCE SEC where JUL.KEY like '%JULIAN%' and SEC.KEY like '%SECOND%';

Question - 144 : - What are Clusters ?

Answer - 144 : - Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

Question - 145 : - What is Statement Auditing ?

Answer - 145 : - Statement auditing is the auditing of the powerful system privileges without regard to specifically named objects.

Question - 146 : - What are visual attributes?

Answer - 146 : - Visual attributes are the font, color, pattern proprieties that you set for form and menu objects that appear in your application interface.

Question - 147 : - How does one put a database into ARCHIVELOG mode?

Answer - 147 : - The main reason for running in archivelog mode is that one can provide 24-hour availability and guarantee complete data recoverability. It is also necessary to enable ARCHIVELOG mode before one can start to use on-line database backups. To enable ARCHIVELOG mode, simply change your database startup command script, and bounce the database: SQLPLUS> connect sys as sysdba SQLPLUS> startup mount exclusive; SQLPLUS> alter database archivelog; SQLPLUS> archive log start; SQLPLUS> alter database open; NOTE1: Remember to take a baseline database backup right after enabling archivelog mode. Without it one would not be able to recover. Also, implement an archivelog backup to prevent the archive log directory from filling-up. NOTE2: ARCHIVELOG mode was introduced with Oracle V6, and is essential for database point-in-time recovery. Archiving can be used in combination with on-line and off-line database backups. NOTE3: You may want to set the following INIT.ORA parameters when enabling ARCHIVELOG mode: log_archive_start=TRUE, log_archive_dest=... and log_archive_format=... NOTE4: You can change the archive log destination of a database on-line with the ARCHIVE LOG START TO 'directory'; statement. This statement is often used to switch archiving between a set of directories. NOTE5: When running Oracle Real Application Server (RAC), you need to shut down all nodes before changing the database to ARCHIVELOG mode.

Question - 148 : - What is a SNAPSHOT ?

Answer - 148 : - Snapshots are read-only copies of a master table located on a remote node which is periodically refreshed to reflect changes made to the master table.

Question - 149 : - What is Distributed database ?

Answer - 149 : - A distributed database is a network of databases managed by multiple database servers that appears to a user as single logical database. The data of all databases in the distributed database can be simultaneously accessed and modified.

Question - 150 : - What are the sql clauses supported in the link property sheet?

Answer - 150 : - Where start with having.

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Rajeev Katiyar
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