DataFlex applications can use data from most databases. The DataFlex embedded database is ISAM-based and the Application Framework and language were built on the ISAM model of data access. In order for DataFlex to function when connecting to other databases, it imposes some requirements on the structure of the data it can connect to. Every table that DataFlex connects to must have the means to uniquely identify individual records (rows) in the table. If a table fails to meet this requirement it cannot be accessed using the Application framework. It can however be accessed using Embedded SQL.
Previous versions of DataFlex and SQL drivers imposed an additional requirement on tables; a table needed "record identity". This requirement has been removed with the introduction of DataFlex 11. A table that meets the record identity requirement is called a recnum table.
The SQL Drivers are able to access data in tables that do not meet the record identity requirement but do meet the less strict requirement of the ability to uniquely identify individual records. Such a table is called a standard table.
Defining the Table Type and Primary Index
Understanding How Connectivity Works