ch01.htm

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<P><FONT COLOR="#000077"><B>Procedure</B></FONT></P>
<P>A procedure 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>Program Unit</B></FONT></P>
<P>In Oracle, program unit is used to describe a package, a stored procedure, or
a sequence.</P>
<P><FONT COLOR="#000077"><B>Query</B></FONT></P>
<P>A query is a read-only transaction against a database. A query is generated using
the <TT>SELECT</TT> statement. Users generally distinguish between queries and other
transaction types because a query does not the change data in the database.</P>
<P><FONT COLOR="#000077"><B>Schema</B></FONT></P>
<P>A schema is a collection of objects associated with the database.</P>
<P><FONT COLOR="#000077"><B>Schema Objects</B></FONT></P>
<P>Schema objects are abstractions or logical structures that refer to database objects
or structures. Schema objects consist of such things as clusters, indexes, packages,
sequences, stored procedures, synonyms, tables, views, and so on.</P>
<P><FONT COLOR="#000077"><B>System Global Area (SGA)</B></FONT></P>
<P>The SGA is a shared-memory region that Oracle uses to store data and control information
for one Oracle instance. The SGA is allocated when the Oracle instance starts; it
is deallocated when the Oracle instance shuts down. Each Oracle instance that starts
has its own SGA. The information in the SGA is made up of the database buffers, the
redo log buffer, and the shared pool; each has a fixed size and is created at instance
startup.</P>
<P><FONT COLOR="#000077"><B>Transaction</B></FONT></P>
<P>A transaction is a logical unit of work consisting of one or more SQL statements,
ending in a commit or a rollback. Performance measurements often use the number of
transactions per second or per minute as the performance metric.</P>
<P><FONT COLOR="#000077"><B>Trigger</B></FONT></P>
<P>A trigger is a mechanism that allows you to write procedures that are automatically
executed whenever an <TT>INSERT</TT>, <TT>UPDATE</TT>, or <TT>DELETE</TT> statement
is executed on a table or view. Triggers can be used to enforce integrity constraints
or automate some other custom function.</P>
<P><FONT COLOR="#000077"><B>Virtual Memory</B></FONT></P>
<P>This term refers to the memory that can be used for programs in the operating
system. To overcome the limitations associated with insufficient physical memory,
virtual memory allows programs to run that are larger than the amount of physical
memory in the system. When there is not enough physical memory in the system, these
programs are copied from RAM to a disk file called a <I>paging</I> or <I>swap</I>
<I>file</I>. This arrangement allows small systems to run many programs. You pay
a performance penalty when the computer pages or swaps.</P>
<P><FONT COLOR="#000077"><B>Storage Units</B></FONT></P>
<P>Data is stored in the computer in a binary form. The units used to refer to this
binary data are as follows:

<DL>
	<DD>
</DL>

<P>
<TABLE BORDER="0">
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP"><B><I>Term</I></B></TD>
		<TD ALIGN="LEFT" VALIGN="TOP"><B><I>Definition</I></B></TD>
		<TD ALIGN="LEFT" VALIGN="TOP"><B><I>Comment</I></B></TD>
	</TR>
	<TR>
		<TD ALIGN="LEFT" VALIGN="TOP">bit</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">The smallest unit of data storage</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">A bit is either a 1 or a 0.</TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">nibble</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">4 bits</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">This term is not commonly used.</TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">byte</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">8 bits</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">The most commonly used storage unit.</TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">word</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">This term is architecture</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">On some systems, a word is 16 bits;</TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">dependent</TD>
		<TD ALIGN="LEFT" VALIGN="TOP">on others, a word is 32 or 64 bits.</TD>
		<TD ALIGN="LEFT" VALIGN="TOP"></TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">kilobyte (KB)</TD>
		<TD ALIGN="LEFT" VALIGN="TOP"></TD>
		<TD ALIGN="LEFT" VALIGN="TOP">Even though <I>kilo</I> usually means 1,000, a kilobyte in computer terms is actually
			1,024 bytes (because we like powers of 2).</TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">megabyte (MB)</TD>
		<TD ALIGN="LEFT" VALIGN="TOP"></TD>
		<TD ALIGN="LEFT" VALIGN="TOP">The term megabyte denotes 1,024KB or 1,048,576 bytes.</TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">gigabyte (GB)</TD>
		<TD ALIGN="LEFT" VALIGN="TOP"></TD>
		<TD ALIGN="LEFT" VALIGN="TOP">A gigabyte is 1,024 megabytes or 1,073,741,824 bytes.</TD>
	</TR>
	<TR ALIGN="LEFT" rowspan="1">
		<TD ALIGN="LEFT" VALIGN="TOP">terabyte (TB)</TD>
		<TD VALIGN="TOP"></TD>
		<TD VALIGN="TOP">A terabyte is 1,024 gigabytes or 1,099,511,627,776 bytes.</TD>
	</TR>
</TABLE>
</P>
<P><BR>
It is not uncommon to hear large data warehousing sites talk in terms of terabytes.
In the next few years, you will probably hear of systems using storage in the tens
and hundreds of terabytes.
<H2><FONT COLOR="#000077"><B>Oracle Configurations</B></FONT></H2>
<P>There are many different types of Oracle configurations and uses. Let's look at
some of these different types of systems and analyze their usage and characteristics.
<H3><FONT COLOR="#000077"><B>OLTP</B></FONT></H3>
<P>The Online Transaction Processing (OLTP) system is probably the most common of
the RDBMS configurations. OLTP systems have online users that access the system.
These systems are typically used for order-entry purposes, such as for retail sales,
credit-card validation, ATM transactions, and so on.
<H4><FONT COLOR="#000077"><B>Characteristics of OLTP Systems</B></FONT></H4>
<P>OLTP systems typically support large numbers of online users simultaneously accessing
the RDBMS. Because users are waiting for data to be returned to them, any excessive
response time is immediately noticeable. OLTP systems are characteristically read
and write intensive. Depending on the specific application, this read/write ratio
might vary.
<H3><FONT COLOR="#000077"><B>DSS</B></FONT></H3>
<P>The Decision Support System (DSS) is used to assist with the decision-making process.
These decisions might be based on information such as how sales in a particular region
are doing, what cross-section of customers is buying a particular product, or to
whom to send a mailing. The DSS system is used to help make decisions by providing
good data.
<H4><FONT COLOR="#000077"><B>Characteristics of a DSS</B></FONT></H4>
<P>The DSS is characterized by long-running queries against a large set of data.
Unlike the OLTP system, where users are waiting for data to return to them online,
here users expect the queries to take minutes, hours, or days to complete. The data
is typically generated from a different source and loaded onto the DSS computer in
bulk. Except for during the load, the DSS system is characterized by being read intensive
(with very few writes).
<H3><FONT COLOR="#000077"><B>Data Warehouse</B></FONT></H3>
<P>A data warehouse is typically considered to be a large-scale system that consists
of both DSS and OLTP components. These systems are typically hundreds of gigabytes
in size and support many users.
<H4><FONT COLOR="#000077"><B>Characteristics of a Data Warehouse</B></FONT></H4>
<P>Data warehouses have some of the attributes of a DSS system, such as long-running
queries and a possible online component. In many cases, this component is the source
of the data used in the DSS queries.
<H3><FONT COLOR="#000077"><B>Data Mart</B></FONT></H3>
<P>A data mart, which is a smaller-scale version of a data warehouse, serves many
of the same functions as a data warehouse.
<H4><FONT COLOR="#000077"><B>Characteristics of a Data Mart</B></FONT></H4>
<P>A data mart is typically 100GB or less in size. As with a data warehouse, a data
mart supports many online users as well as a decision-support function.
<H3><FONT COLOR="#000077"><B>Video Server</B></FONT></H3>
<P>A video server can support large numbers of video data streams. These video streams
can be used for purposes such as video on demand for entertainment as well as training
functions.
<H4><FONT COLOR="#000077"><B>Characteristics of a Video Server</B></FONT></H4>
<P>The video server system must support a high network bandwidth in order to support
multiple data streams. The video server must also be able to support a high I/O bandwidth.
These disk accesses are typically of a very large block size and sequential in nature.
<H3><FONT COLOR="#000077"><B>Web Server</B></FONT></H3>
<P>The Oracle Web server is designed to support both static and dynamic Web pages.
These pages can be simple Web pages or complex database-generated pages. Oracle Web
server systems are also typically used in Web commerce applications. These installations
can allow the customer to browse online catalogs, which might feature graphics or
even video. The customer can then purchase items online.
<H4><FONT COLOR="#000077"><B>Characteristics of an Oracle Web Server</B></FONT></H4>
<P>The Oracle Web server typically supports many online users. There is typically
a large amount of data that has been accessed frequently and other data that is less
frequently accessed. A large amount of memory can help improve performance in this
type of configuration.
<H3><FONT COLOR="#000077"><B>OLAP</B></FONT></H3>
<P>The term OLAP (Online Analytical Processing) is usually used in relation with
multidimensional data. OLAP users might be financial analysts or marketing personnel
looking at global data.
<H4><FONT COLOR="#000077"><B>Characteristics of an OLAP System</B></FONT></H4>
<P>An OLAP system typically involves a large amount of disk space with heavy I/O
and memory requirements. An OLAP system might support only a few or many users. This
depends on your type of configuration.
<H2><FONT COLOR="#000077"><B>Roles and Responsibilities of an Oracle DBA</B></FONT></H2>
<P>If you want to become an Oracle DBA, you should first understand what an Oracle
DBA's job is. The basic roles of the DBA are fairly consistent among different companies,
but these duties might be expanded based on the size of the company and the experience
of the DBA. In fact, the DBA is considered the main resource for DBMS experience
and knowledge in many companies.</P>