The Vo2Ado RDD > Basics > Table files or Table Callback

A very important difference between the regular RDDs and the Vo2Ado RDD is that the RDD does not store its information in tables on the users harddisk or network drive, but in a table on a server computer. This information generally is not directly accessible for the worskstation, but needs to be retrieved through ADO.

Therefore there usually is no file visible for the application that can be opened by the application. The RDD also does not need such a file, because it can use a special callback mechanism to ask the application all the information that it needs to open the table.

Unfortunately some RDD based applications are file based, which means that they offer you a standard file dialog to open a DBF file.

A sample of such an application is the VO Standard framework, and also an application such as the DBServer Editor in VO and 3rd party products such as ReportPro.

To be able to work with applications that are designed like this we have introduced a set of special ADO Files in the familiar INI file layout.

•the so called Ado Data file with an ADF extension. This file contains the table name and connection name and other information needed to open a specific data table

•a file called CONFIG.ADO that contains Connection information and Provider information

Please rember that for normal use of the RDD you do not need these files, because you can handle everything through a callback mechanism in your application.

If you do need an ADF file, you can create this them autmatically when you have opened a file in your application by calling the DbInfo function (Info method on the DbServer class) with the following parameters:

•DBI_SAVETABLEDEF

•The filename to create

A sample of this could be:

RddSetDefault("VO2ADO")

USE Employee

DBInfo(DBI_SAVETABLEDEF, "Employee")

or call the support function from the Vo2Ado RDD Support Library:

AdoDbSaveTableDef("Employee")

This will create the Employee.ADF file, See the topic table file structure for more information about the contents of this file

To create a CONFIG.ADO file you we have implemented a similar approach:

call the DbInfo function (Info method on the DbServer class) with the following parameters:

•DBI_SAVECONNECTION

•The filename to create (default is CONFIG.ADO in the same folder as the ADF file

•

A sample of this could be:

RddSetDefault("VO2ADO")

USE Employee

DBInfo(DBI_SAVETABLEDEF, "Employee")

DBInfo(DBI_SAVECONNECTION )

or call the support function from the Vo2Ado RDD Support Library:

AdoDbSaveConnection()

See the topic connection file structure for more information about the contents of this file.