New Document
Computer Science
Computer Catlog
Oracle Catlog

History of Oracle
Introduction to Terms
Oracle Configurations
Roles of Database Administrator
Oracle Architecture
A Brief History of SQL
Dr. Codd's 12 Rules
An Overview of SQL
The SELECT Statement
Expressions, Conditions, and Operators
Functions
Clauses in SQL
Joining Tables
Sub Query
Manipulating Data
Building a Database
Views and Indexes
Controlling Transactions
Database Security
Advanced SQL Topics
Cursors
Stored Procedures
Triggers
Embedded SQL
SQL Tuning
Using Views in Data Dictionary
Using SQL to Generate SQL Statements

Question & Answer



Q) What units of measurement are typically used in databases? A With Oracle systems you usually discuss size in terms of megabytes and gigabytes, but some systems are growing into the terabyte range.

    A) No, far from it. No two sites are the same. Although the basic duties and responsibilities might be similar, the extended duties are always different.


Q) Why is it important to document?

    A)If you document the system configuration and logging changes, you will have a much easier time reproducing the system in the event of a failure. By having configuration information in a log book you can save numerous hours of trial and error in reconfiguring the system.


Q) What are the main hardware components that affect performance?

    A)The main hardware components that affect performance are the speed of the CPU(s), the amount of memory, and the I/O subsystem.


Q) What happens if a failure corrupts the redo log files?

    A)If redo log files are lost, you cannot recover the database. All changes made since the last backup will be lost. This is why redo log files should be on protected or fault-tolerant disk drives.


Q)What happens if a failure corrupts the datafiles?

    A)When a datafile is lost, the corrupted file can be restored from a backup. After the datafile is restored, the redo log files and archive log files can reapply any changes made before the time of the failure. No data is lost.


Q) Why does parallelizing a query make things faster?

    A)Most of the realtime or clock-time processing a query operation is spent waiting for I/Os to complete. Parallelizing a query enables you to keep the CPUs busy while you are waiting.