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<FONT COLOR="#000077">Teach Yourself Oracle 8 In 21 Days</FONT></H1>
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<H1><FONT COLOR="#000077">- Day 1 -<BR>
Starting Out with Oracle</FONT></H1>
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<P>Being an Oracle database operator or administrator can be a demanding but rewarding
career that carries with it a great deal of responsibility as well as authority.
This book is intended to help you embark on this exciting path. I hope that within
the pages of this book I can convey some of the enthusiasm and excitement I feel
when working with state-of-the-art hardware and software such as Oracle8.</P>
<P>I think the best way to grasp a concept is to fully understand why actions are
taken and the consequences of those actions. If you understand how Oracle works and
its interactions with the operating system and hardware, you can more easily predict
and anticipate the result of actions you take. In this book, I attempt to fully explain
the workings of Oracle and the supporting software and hardware.
<H2><FONT COLOR="#000077"><B>A Brief History of Oracle</B></FONT></H2>
<P>In 1977, Larry Ellison, Bob Miner, and Ed Oates formed a company called Relational
Software Incorporated (RSI). This company built an RDBMS called <I>Oracle</I>. Ellison,
Miner, and Oates made a key decision: to develop their RDBMS using C and the SQL
interface. Soon after, they came out with version 1, a prototype. In 1979, RSI delivered
its first product to customers. The Oracle RDBMS version 2 worked on the Digital
PDP-11 running the RSX-11 operating system and was soon ported to the DEC VAX system.</P>
<P>1983 heralded the release of version 3, which touted changes in the SQL language
as well as performance enhancements and other improvements. Unlike earlier versions,
version 3 was written almost entirely in C. At this point, RSI changed its name to
Oracle Corporation.</P>
<P>Oracle version 4 was released in 1984. This version supported both the VAX system
and the IBM VM operating system. Version 4 was the first version to incorporate read
consistency. Version 5, introduced in 1985, was a milestone because it introduced
client/server computing to the market with the use of SQL*Net. Version 5 was also
the first MS-DOS product to break through the 640KB barrier.</P>
<P>In 1988, Oracle presented version 6, which introduced low-level locking as well
as a variety of performance improvements and functionality enhancements, including
sequence generation and deferred writes. I was introduced to Oracle6 back in the
days when we ran the TP1, TPC-A, and TPC-B benchmarks. At this point, Oracle was
running on a large variety of different platforms and operating systems. In 1991,
Oracle introduced the Oracle Parallel Server option on version 6.1 of the Oracle
RDBMS on the DEC VAX platform. Soon the Parallel Server option was available on a
variety of platforms.</P>
<P>Oracle7, released in 1992, included many architectural changes in the area of
memory, CPU, and I/O utilization. Oracle7 is the full-featured RDBMS to which you
are accustomed, the one you've been using for many years. Oracle7 introduced many
advances in the area of ease of use, such as the SQL*DBA tools and database roles.</P>
<P>Finally, in 1997 Oracle introduced Oracle8, which added object extensions as well
as a host of new features and administrative tools.</P>
<P>For more information about the history of Oracle (specifically about the Oracle
server), check out the two-part article by Ken Jacobs in the January/February and
March/April 1995 issues of <I>Oracle Magazine</I>.</P>
<P>For more information about the Oracle corporation, its products, and about working
with Oracle, check out <TT>www.oracle.com</TT>. This Web site contains a wealth of
information about Oracle parterships and products as well as information about the
Oracle Developer Program, which specifically assists developers.
<H2><FONT COLOR="#000077"><B>Introduction to Terms</B></FONT></H2>
<P>Many different terms and concepts will be used throughout this book. I've introduced
them here to make it easier for you to grasp many of the concepts and lessons to
follow. If you encounter other terms with which you are unfamiliar, check out Appendix
D, "Glossary."</P>
<H4><FONT COLOR="#000077"><B>Ad-Hoc Query</B></FONT></H4>
<P>This use of the Latin term means an impromptu, simple query.</P>
<H4><FONT COLOR="#000077"><B>Block</B></FONT></H4>
<P>A block is the smallest unit of storage in an Oracle database. The database block
contains header information concerning the block itself as well as the data or PL/SQL
code. The Oracle block size is configurable with the minimum size being 2KB and the
maximum size being 16KB.</P>
<P><FONT COLOR="#000077"><B>Bottleneck</B></FONT></P>
<P>In computer terms, a bottleneck is a system component that limits the performance
of the system.</P>
<P><FONT COLOR="#000077"><B>Buffer</B></FONT></P>
<P>This term refers to an amount of memory used to store data. A buffer stores data
that is about to be used or that has just been used. In many cases, buffers are in-memory
copies of data that is also on disk. Buffers can be used as a copy of data for quick
read access, they can be modified and written to disk, or they can be created in
memory as temporary storage.</P>
<P>In Oracle, database buffers of the SGA store the most recently used blocks of
database data. The set of database block buffers is known as the <I>database buffer
cache</I>. The buffers used to temporarily store redo entries until they can be written
to disk are known as <I>redo log buffers</I>.</P>
<P><FONT COLOR="#000077"><B>Cache</B></FONT></P>
<P>A cache is a storage area used to provide fast access to data. In hardware terms,
the cache is a small (relative to main RAM) amount of memory that is much faster
than main memory. This memory is used to reduce the time it takes to reload frequently
used data or instructions into the CPU. CPU chips themselves contain small amounts
of memory built in as cache.</P>
<P>In Oracle, the block buffers and shared pool are considered caches because they
are used to store data and instructions for quick access. Caching is very effective
in reducing the time it takes to retrieve frequently used data.</P>
<P>Caching usually works using a least recently used algorithm. Data that has not
been used for a while is eventually released from the cache to make room for new
data. If data is requested and is in the cache (a phenomenon called a <I>cache hit</I>),
the data is retrieved from the cache, preventing it from having to be retrieved from
memory or disk. After the data has been accessed again, it is marked as recently
used and put on the top of the cache list.</P>
<P><FONT COLOR="#000077"><B>Checkpoint</B></FONT></P>
<P>A checkpoint is an operation that forces all changed, in-memory data blocks to
be written out to disk. This is a key factor in how long the database takes to recover
in the event of a failure. This concept is discussed in depth on Day 2, "Exploring
the Oracle Architecture."</P>
<P><FONT COLOR="#000077"><B>Clean Buffer</B></FONT></P>
<P>A <I>clean buffer</I> is a buffer that has not been modified. Because this buffer
has not been changed, it is not necessary for the DBWR to write this buffer to disk.</P>
<P><FONT COLOR="#000077"><B>Concurrency</B></FONT></P>
<P>This term refers to the capability to perform many functions at the same time.
Oracle provides for concurrency by allowing many users to access the database simultaneously.</P>
<P><FONT COLOR="#000077"><B>Database</B></FONT></P>
<P>A database is a set of data, organized for easy access. The database is the actual
data. It is the database that you will be accessing when you need to retrieve data.</P>
<P><FONT COLOR="#000077"><B>Data Dictionary</B></FONT></P>
<P>The data dictionary is a set of tables Oracle uses to maintain information about
the database. The data dictionary contains information about tables, indexes, clusters,
and so on.</P>
<P><FONT COLOR="#000077"><B>DBA (Database Administrator)</B></FONT></P>
<P>The DBA is the person responsible for the operation, configuration, and performance
of the database. The DBA is charged with keeping the database operating smoothly,
ensuring that backups are done on a regular basis (and that the backups work), and
installing new software. Other responsibilities might include planning for future
expansion and disk space needs, creating databases and tablespaces, adding users
and maintaining security, and monitoring the database and retuning it as necessary.
Large installations might have teams of DBAs to keep the system running smoothly;
alternatively, the tasks might be segmented among the DBAs.</P>
<P><FONT COLOR="#000077"><B>DBMS or RDBMS</B></FONT></P>
<P>The Database Management System is the software and collection of tools that manages
the database. Oracle software is the DBMS. A Relational Database Management System
is a DBMS that is relational in nature. This means that the internal workings access
data in a relational manner. Oracle is an RDBMS.</P>
<P><FONT COLOR="#000077"><B>DDL (Data Definition Language) Commands</B></FONT></P>
<P>These commands are used in the creation and modification of schema objects. These
commands provide the ability to create, alter, and drop objects; grant and revoke
privileges and roles; establish auditing options; and add comments to the data dictionary.
These commands are related to the management and administration of the Oracle database.
Before and after each DDL statement, Oracle implicitly commits the current transaction.</P>
<P><FONT COLOR="#000077"><B>Dirty Buffer</B></FONT></P>
<P>A <I>dirty buffer</I> is a buffer that has been modified. It is the job of the
DBWR to eventually write all dirty block buffers out to disk.</P>
<P><FONT COLOR="#000077"><B>DML (Data Manipulation Language) Commands</B></FONT></P>
<P>These commands allow you to query and modify data within existing schema objects.
Unlike the DDL commands, a commit is not implicit. DML statements consist of <TT>DELETE</TT>,
<TT>INSERT</TT>, <TT>SELECT</TT>, and <TT>UPDATE</TT> statements; <TT>EXPLAIN PLAN</TT>
statements; and <TT>LOCK TABLE </TT>statements.</P>
<P><FONT COLOR="#000077"><B>Dynamic Performance Tables</B></FONT></P>
<P>These tables are created at instance startup and used to store information about
the performance of the instance. This information includes connection information,
I/Os, initialization parameter values, and so on.</P>
<P><FONT COLOR="#000077"><B>Function</B></FONT></P>
<P>A function is a set of SQL or PL/SQL statements used together to execute a particular
function. Procedures and functions are identical except that functions always return
a value (procedures do not). By processing the SQL code on the database server, you
can reduce the number of instructions sent across the network and returned from the
SQL statements.</P>
<P><FONT COLOR="#000077"><B>IM (Information Management)</B></FONT></P>
<P>This term is usually used to describe the department that handles your corporate
data.</P>
<P><FONT COLOR="#000077"><B>IS (Information Systems)</B></FONT></P>
<P>This term is also used to describe the department that handles your corporate
data.</P>
<P><FONT COLOR="#000077"><B>IT (Information Technology)</B></FONT></P>
<P>This term is used to describe the business of managing information.</P>
<P><FONT COLOR="#000077"><B>Network Computing Architecture (NCA)</B></FONT></P>
<P>The Network Computing Architecture is a standard for computing over the network.
The NCA was developed in conjunction with Oracle.</P>
<P><FONT COLOR="#000077"><B>Physical Memory</B></FONT></P>
<P>This term refers to the actual hardware RAM (Random Access Memory) available in
the computer for use by the operating system and applications.</P>
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