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<concept id="GUID-21CF1D5F-44C5-5407-B3C9-8BC103C97079" xml:lang="en"><title>File

Stores Overview</title><shortdesc>Provides a summary of APIs related to the File Store and their

uses.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-D44D9C54-8783-4D88-A7D8-F25FFE754802"><title>Purpose</title> <p>Provides

file-based structured data storage, using networks of streams.</p> </section>

<section id="GUID-C7FB5BC3-D5FE-451D-990C-E68F28215A4C"><title>Architectural

relationships</title> <p>The File Stores API is based on the abstract store

types defined by the Stores API. The underlying file handling is provided

by the File Server.</p> <p>The permanent file stores defined in this API are

used by the relational database API, DBMS, for data storage.</p> </section>

<section id="GUID-AD9259E7-ABE2-4EE7-B316-7B24EBE5353E"><title>Description</title> <p>The

API has five key concepts: file store base (<codeph>CFileStore</codeph>),

direct file store (<codeph>CDirectFileStore</codeph>), permanent file store

(<codeph>CPermanentFileStore</codeph>), dictionary file store (<codeph>CDictionaryFileStore</codeph>),

and file streams (<codeph>RFileWriteStream</codeph> and <codeph>RFileReadStream</codeph>).</p> <p><b>File

store base</b> </p> <p>This abstract base class provides basic behaviour for

file stores, such as reading a store from a specified file. </p> <p>File stores

are derived from the persistent store base (<codeph>CPersistentStore</codeph>)

provided by the Stores API. This means that they have a root stream, from

which all other streams within the store can be found.</p> <p>The file store

base class is <codeph>CFileStore</codeph>.</p> <p><b>Direct file store</b> </p> <p>A

direct file store implements a file store in which once the streams have been

committed and closed, they cannot subsequently be changed. They are used by

the type of application that treats the in-memory copy of its data as its

prime copy, and on saving, replaces the entire store. </p> <p>The direct file

store is a concrete type, derived from <codeph>CFileStore</codeph>, and is

provided by <codeph>CDirectFileStore</codeph>.</p> <p><b>Permanent file store</b> </p> <p>A

permanent file store implements a file store in which existing streams within

the store can be changed. They are used by the type of application which treats

the data in the store as its prime copy. Typically, the object network comprising

the application’s data is structured so that sections of data can be loaded

in, and, if changed, written back to the store. Memory is used as a workplace

for changing data.</p> <p>The permanent file store is a concrete type, derived

from <codeph>CFileStore</codeph>, and is provided by <codeph>CPermanentFileStore</codeph>.</p> <p><b>Dictionary

file store</b> </p> <p>The dictionary file store implements a dictionary store,

a network of streams each of which can be accessed via a UID, in file storage.</p> <p>The

dictionary file store is a concrete type, derived from <codeph>CDictionaryStore</codeph>,

and is provided by <codeph>CDictionaryFileStore</codeph>.</p> <p><b>File streams</b> </p> <p>File

streams allow standard files (<xref href="GUID-BE0804F6-4375-3C8A-8C83-968F510466E0.dita"><apiname>RFile</apiname></xref> objects as defined

in the File Server Client Side API), not file stores, to be written to as

streams. This can be simpler and more efficient than using the equivalent <xref href="GUID-BE0804F6-4375-3C8A-8C83-968F510466E0.dita"><apiname>RFile</apiname></xref> functions. </p> <p>The

file stream classes are <codeph>RFileReadStream</codeph> and <codeph>RFileWriteStream</codeph>.</p> </section>

</conbody><related-links>

<linklist>

<link href="GUID-5EAED550-5FFC-54A6-BB4A-720975B127B8.dita"><linktext>Stores Overview</linktext>

</link>

<link href="GUID-66ACFC54-5671-5B72-9DBC-A76F7A112D63.dita"><linktext>Store Streams

Overview</linktext></link>

<link href="GUID-744ACF2C-963B-5E2F-A6B3-220AB899FD23.dita"><linktext>Streaming

Overview</linktext></link>

<link href="GUID-13C95985-D16F-5A9E-A7F8-CAB637C4C6ED.dita"><linktext>DBMS Overview</linktext>

</link>

</linklist>

</related-links></concept>