The UNICOM Intelligence Data File CDSC reads and writes case data to a UNICOM Intelligence file-based database that has a .ddf extension. The UNICOM Intelligence Data File CDSC provides all the features of the Relational MR database (RDB) CDSC, but does not require a separate relational database management system. UNICOM Intelligence Data Files therefore provide a simpler and more portable format for the storage of "offline" UNICOM Intelligence Interviewer data.

The UNICOM Intelligence Data File CDSC provides the following features:

The UNICOM Intelligence Data File CDSC is intended for use with single/multi-user read and single-user read/write applications. The CDSC has not been tested with applications that perform concurrent multi-user write operations. For more information, see SQLite and multiple users.

The UNICOM Intelligence Data File CDSC can be used for fast merge of data that matches certain criteria. For more information, see DDF Merge Utility.

The internal name of this DSC is mrDataFileDsc.

If the UNICOM Intelligence Data File specified in the connection string does not exist, the UNICOM Intelligence Data File CDSC will create a new file.

If the file specified in the connection string already exists, and the value of the MR Init Overwrite connection property (see Connection properties) is 0, any new rows written to the file are appended to the existing data. In this situation, the UNICOM Intelligence Data File CDSC adds columns and tables to the internal schema of the file as necessary to store variables that were not present in the existing data.

Each level can have a maximum of 32,674 fields; this limit is because of the underlying SQLITE maximum columns setting. The limit is based on the number of fields at a level, not the number of variable instances. It applies to both read and export. If this limit is exceeded, a “Failed to create the column 'column_name'” error occurs.