2.2.1 Single-tier Components

2.2.1 Single-tier Components

The elements of AcuODBC single tier are the following:

The ODBC driver manager

The ODBC driver for ACUCOBOL-GT data (ACUV32.DLL)

The data dictionary files generated by your ACUCOBOL-GT compiler

Local ACUCOBOL-GT data files (Vision or relative)

ODBC Driver Manager

The ODBC driver manager is typically provided by Microsoft. Its function is to receive calls from the Windows application, establish which data source driver is being used, call the driver (in this case, the Vision driver, AcuODBC), and load it into memory if it is not already there.

For Microsoft Windows 95, Windows 98, and Windows NT environments, the 32-bit driver manager is ODBC32.DLL.

Most often, the driver manager is included with the ODBC application driver and is installed along with the application. For some products, such as Microsoft Excel, the driver manager is installed automatically if you choose the ODBC support option while installing the product. (The ODBC support option tends to be part of the "custom" install process.)

AcuODBC requires Version 2.0 or later of Microsoft's ODBC Driver Manager. If you do not already have this version installed, you may install it from the AcuODBC installation disks.

ODBC Driver for ACUCOBOL-GT Data

The ODBC driver for ACUCOBOL-GT data--known as AcuODBC--is provided by Acucorp on your AcuODBC installation disks in the form of a dynamic link library, ACUV32.DLL. The license file included on your installation disks determines whether or not your driver can access remote files via AcuServer^TM.

Note: If you plan to access remote files using AcuODBC, you must have WSOCK32.DLL installed on the client machine and a licensed copy of AcuServer installed on the server. WSOCK32.DLL is available as a free download from Microsoft, and it comes automatically with TCP/IP software such as PC/TCP and Chameleon.

The function of the ODBC driver for ACUCOBOL-GT is to receive SQL commands from the ODBC driver manager, and translate them from SQL to Vision or relative file I/O using Acucorp's data dictionary files.

Data Dictionaries

Because the ODBC standard typically involves relational databases, ODBC-enabled applications execute calls to databases using SQL. While SQL databases handle I/O at the column (field) level, COBOL handles I/O at the record level. For this reason, AcuODBC must map database fields into COBOL records, and map the COBOL records back into database fields.

To perform field/record mapping, AcuODBC consults data dictionaries that are automatically generated by the ACUCOBOL-GT compiler. These files are known as extended file descriptors, or XFDs, and are created whenever you compile with the "-Fx" or "-Fxa" option. The detailed structure of data dictionaries is discussed in Section 7.2.1 How the Data Dictionary is Formed.