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<concept id="GUID-A19A1F43-E42B-5FC2-AE58-A7BC67B6733A" xml:lang="en"><title>Migrating

from CommDb to the CommsDat API</title><shortdesc>This section highlights some of the issues in the migration from

the CommDb to the CommsDat API. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The CommsDat API replaces CommDb. Users of CommDb do not need to make changes

to their code. Symbian platform provides a shim that translates the calls

to the CommDb API to calls to the CommsDat API. </p>

<p>The CommDb API will be withdrawn in the future. Developers are recommended

to migrate to the CommsDat API. </p>

<section id="GUID-BAAA18F6-2276-4F0A-A705-7E48D28CD452"><title>Removal of the CommDb SQL API</title> <p>The Commdb SQL API

is removed. </p> <p>The CommDb API allows tools and applications to select

views of database tables that match field values. The CommDb API also allows

tools and applications to create new user defined tables in the database at

run time. </p> <p>The CommsDat keeps this behaviour. Tools and applications

can select sets of records by pattern matching fields in a primed table, record

or field object with records in the database. Tools and applications can also

use the CommsDat API to define and store user defined records. </p> </section>

<section id="GUID-DC5B7004-27F4-4883-ABBA-0747EE90738E"><title>Referring to database elements by Id instead of by       

   Name</title> <p>The Commdb API has an interface based on column names.

This method is not efficient. </p> <p>The CommsDat API allows tools and applications

to find elements in the database by numeric id and to provide direct access

through mapped data objects. You can continue to find elements in the Comms

Database by name. The Nifman API continues to use this method. This method

is not recommended, because it is very inefficient. </p> </section>

<section id="GUID-1452DF5C-BF8B-4103-8DBB-3DD41BD2370B"><title>Retrieving small amounts of data</title> <p>Tools and applications

do not need to simulate the use of a whole view when they use the <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CMDBRecordSet</apiname></xref> &lt;T&gt; class. Tools and applications

can use <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>CMDBRecordSet</apiname></xref> &lt;T&gt; objects

for data retrieval. </p> </section>

<section id="GUID-B5926C0D-AAE9-4030-B35B-E2D616E81768"><title>Use record tags instead of record names in user defined  

        fields</title> <p>Many CommDb searches are for records by user defined

record name. This type of search is not efficient. </p> <p>The use of numeric

Ids improves the performance of searches. User defined records can define

a record tag field. Tools and applications give this field the unique numeric

Id <xref href="GUID-1CDD0B97-8B00-3373-9908-512C9BC1CF51.dita"><apiname>KCDTIdRecordTag</apiname></xref>. Current procedure

fills this field with the record Id of the record. This procedure provides

backward compatibility with CommdbId. The field value can be any numeric record

tag. For example, a <keyword>UID</keyword> value gives a convenient way to

link records . </p> <p>See <xref href="GUID-A96ABD2C-A338-58E5-A674-E840B1F53670.dita">Creating

a User Defined Table: Tutorial</xref>  </p> </section>