An ESQL preprocessor is essentially a conversion tool called by the COBOL compiler that processes embedded SQL, and can convert embedded SQL into code that is understood by your target database. Visual COBOL provides these database access preprocessors from which to choose, all designed to work closely with the Micro Focus COBOL Compiler.
The OpenESQL preprocessor is the most flexible of the three available in Visual COBOL. Use it for basic SQL applications, applications designed to use multiple relational database systems, and for applications you might want to update to use a different relational database system in the future. In addition to processing embedded SQL statements, the OpenESQL preprocessor converts COBOL data types to their equivalent SQL data types.
The DB2 ECM preprocessor converts embedded SQL statements into the appropriate calls to DB2 database services. Use this preprocessor for applications that access a DB2 relational database.
COBSQL is an integrated preprocessor designed to work with COBOL precompilers supplied by the Oracle, Sybase, and Informix relational database vendors. Use COBSQL if you are already using one of these precompilers with an earlier version of a Micro Focus COBOL product and want to migrate your application(s) to Visual COBOL. For any other type of embedded SQL application development, we recommend that you use OpenESQL.
This preprocessor replaces embedded SQL statements with the appropriate calls to database services, and adds code to bind COBOL host variables to the SQL variable names known to the database system.
When using the COBSQL precompiler with Visual COBOL, you can debug programs from the original source code rather than from the code produced by the precompiler.