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<concept id="GUID-13C95985-D16F-5A9E-A7F8-CAB637C4C6ED" xml:lang="en"><title>DBMS

Overview</title><shortdesc>Provides an interface to relational databases. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-40E204A0-AAE5-46AA-BC88-2A80D81AC710"><title>Purpose</title> <p id="GUID-844F756E-1670-5D24-8D63-2092ABE3354C"> The

DBMS component provides an interface to relational databases. It enables you

to create and access databases either from a single client or from multiple

clients sharing access over a server. </p> </section>

<section id="GUID-AC97ABD1-CD17-403B-B654-91A75A6C627A"><title>Required background</title> <p>To use DBMS you need a knowledge

of relational databases and the SQL query language. </p> </section>

<section id="GUID-B0F498B6-722A-4FE2-B7B2-5064FEFF9470"><title>Key concepts and terms</title> <dl>

<dlentry>

<dt>Store database </dt>

<dd><p>A client-side single client database stored in permanent file stores,

implemented by <xref href="GUID-F4A68645-2265-307F-B951-8295827E000B.dita"><apiname>RDbStoreDatabase</apiname></xref>  </p> </dd>

</dlentry>

<dlentry>

<dt>Named database </dt>

<dd><p>A database allowing simultaneous read/write access by multiple clients,

implemented by <xref href="GUID-6433D7F9-B4C7-39DA-BEF4-5EA22B8478A2.dita"><apiname>RDbNamedDatabase</apiname></xref>  </p> </dd>

</dlentry>

</dl> </section>

<section id="GUID-856FC618-CF46-4735-B90B-B1BDB91F01D5"><title>Architecture</title> <p>DBMS defines a general relational

database access API, and allows different database implementations to be provided

of which there are two: a small and relatively lightweight client-side implementation;

and, for when multiple clients must have write access to a database, a client-server

implementation. </p> <p>When multiple clients can access the same database,

transactions ensure that only one client can change data at a time. </p> <p>The <xref href="GUID-21CF1D5F-44C5-5407-B3C9-8BC103C97079.dita">File Stores</xref> API defines

a sophisticated file storage, called permanent file stores, that allows individual

entries in a file to be modified. The database implementations use these stores

for the underlying data storage. </p> <fig id="GUID-6907C48E-3E72-5FED-B5E5-67C6F6922ED9">

<title>              DBMS Class Diagrams           </title>

<image href="GUID-6A482ACB-D39E-578B-B58B-44E4142A5897_d0e590745_href.png" placement="inline"/>

</fig> </section>

<section id="GUID-CC1087EA-0995-4ABE-8C28-8CBF0D62E7FA"><title>DBMS Summary</title> <p>DBMS provides the following: </p> <ul>

<li id="GUID-CA46F9A6-15C2-5584-A907-9D1DD79C8711"><p> <b>Database Management

System Library</b>  </p> <p> <filepath>edbms.dll</filepath>  </p> </li>

<li id="GUID-8D01F878-BCA7-5F88-AC31-BEA68B0739CD"><p> <b>Database Management

System Server</b>  </p> <p> <filepath>edbsrv.exe</filepath>  </p> </li>

</ul> </section>

<section id="GUID-8534CB50-0E49-4614-883B-61B6B583ABCB"><title>APIs</title> <table id="GUID-E682487D-23AC-5A0A-89F5-568D73452AF1">

<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

<thead>

<row>

<entry>API</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><p> <xref href="GUID-E11B1981-CA78-3660-AE09-AD3B4D453733.dita"><apiname>RDbDatabase</apiname></xref>  </p> </entry>

<entry><p>Abstract database class. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-F4A68645-2265-307F-B951-8295827E000B.dita"><apiname>RDbStoreDatabase</apiname></xref>  </p> </entry>

<entry><p>Implements <codeph>RDbDatabase</codeph> as a store database. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-6433D7F9-B4C7-39DA-BEF4-5EA22B8478A2.dita"><apiname>RDbNamedDatabase</apiname></xref>  </p> </entry>

<entry><p>Implements a named database. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-F861EB8F-F621-3E77-8F9A-5E4EFC4E9C2F.dita"><apiname>RDbRowSet</apiname></xref>  </p> </entry>

<entry><p>The base class for all rowset types. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-90ABFA73-6374-367C-BAA9-88CD810035CC.dita"><apiname>RDbTable</apiname></xref>  </p> </entry>

<entry><p>Provides access to table data as a rowset. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-AE1BEF00-5AA7-3F03-95B0-9E40395EDA6C.dita"><apiname>RDbView</apiname></xref>  </p> </entry>

<entry><p>Generates rowsets from an SQL query. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-A7C9FEFA-A9A9-357F-AF66-FA3A288AF925.dita"><apiname>TDbQuery</apiname></xref>  </p> </entry>

<entry><p>A wrapper for an SQL string combined with a text comparison mode. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-E53A90DF-3589-34BD-B7C3-02371567AF41.dita"><apiname>TDbWindow</apiname></xref>  </p> </entry>

<entry><p>Describes the desired shape of a view's pre-evaluation window. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-53AB4535-A859-3A8C-8344-53865B2FE0B4.dita"><apiname>RDbNotifier</apiname></xref>  </p> </entry>

<entry><p>Provides notification of database changes to clients. </p> </entry>

</row>

</tbody>

</tgroup>

</table> </section>

<section id="GUID-B73210AC-8B93-430A-8E6F-8FD06C631E90"><title>Typical uses</title> <p>DBMS is very well suited to applications

with small to medium-sized datasets, where the total record count is less

than 10,000 and the database size is less than 512KB. It scales reasonably

well to larger datasets with total record counts less than 100,000 and database

sizes less than 10MB. </p> <p>DBMS is a suitable database engine for applications

such as: </p> <ul>

<li id="GUID-3638AC16-C761-5FEE-BFE1-C516C5674C88"><p>address books </p> </li>

<li id="GUID-7C3E01B0-898A-5FC0-9C48-EB7D998C878D"><p>call logs </p> </li>

<li id="GUID-B8F92167-446A-5CB0-A5A6-998B2E1ED9A4"><p>message stores. </p> </li>

</ul> </section>

</conbody><related-links>

<link href="GUID-F4875493-6501-56FC-90E5-5EEAA89A72C3.dita"><linktext>Persistent

Storage Overview</linktext></link>

<link href="GUID-12CB6E0E-69CD-51A6-8966-3621CB26E1CD.dita"><linktext>DBMS

rowsets overview</linktext></link>

<link href="GUID-7BE83158-B818-57E4-9A8C-43E5D2C84687.dita"><linktext>DBMS columns,

column sets, and                 keys overview</linktext></link>

<link href="GUID-C61B979A-921A-5756-8D7E-691C3DDD3437.dita"><linktext>DBMS sharing

databases                 overview</linktext></link>

<link href="GUID-120163D6-2E49-5D91-A746-2C8C4C944461.dita"><linktext>DBMS incremental

operations                 overview</linktext></link>

<link href="GUID-21CF1D5F-44C5-5407-B3C9-8BC103C97079.dita"><linktext>File stores

overview</linktext></link>

</related-links></concept>