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Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

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CHAPTER 3<br />

■ ■ ■<br />

Files<br />

In this chapter, we will examine the eight file types that make up a database <strong>and</strong> instance.<br />

The files associated with an instance are simply<br />

• Parameter files: These files tell the <strong>Oracle</strong> instance where to find the control files, <strong>and</strong><br />

they also specify certain initialization parameters that define how big certain memory<br />

structures are, <strong>and</strong> so on. We will investigate the two options available for storing database<br />

parameter files.<br />

• Trace files: These are diagnostic files created by a server process generally in response to<br />

some exceptional error condition.<br />

• Alert file: This is similar to a trace file, but it contains information about “expected”<br />

events, <strong>and</strong> it also alerts the DBA in a single, centralized file of many database events.<br />

The files that make up the database are<br />

• Data files: These files are for the database; they hold your tables, indexes, <strong>and</strong> all other<br />

segments.<br />

• Temp files: These files are used for disk-based sorts <strong>and</strong> temporary storage.<br />

• Control files: These files tell you where the data files, temp files, <strong>and</strong> redo log files are, as<br />

well as other relevant metadata about their state.<br />

• Redo log files: These are your transaction logs.<br />

• Password files: These files are used to authenticate users performing administrative<br />

activities over the network. We will not discuss these files in any detail.<br />

Starting in <strong>Oracle</strong> 10g, there are a couple of new optional file types that are used by <strong>Oracle</strong><br />

to facilitate faster backup <strong>and</strong> faster recovery operations. These two new files are<br />

• Change tracking file: This file facilitates a true incremental backup of <strong>Oracle</strong> data. It<br />

does not have to be located in the Flash Recovery Area, but as it relates purely to database<br />

backup <strong>and</strong> recovery we’ll discuss it in the context of that area.<br />

• Flashback log files: These files store “before images” of database blocks in order to facilitate<br />

the new FLASHBACK DATABASE comm<strong>and</strong>.<br />

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