Specifying CCSIDs for COBOL applications when using the Db2 coprocessor

If you are using the Db2 coprocessor to prepare a COBOL application with SQL statements, use the COBOL compiler to specify the CCSID of the application source code. For optimal performance, use Db2 to specify the CCSID of the application data in SQL statements.

To specify CCSIDs for COBOL applications when using the Db2 coprocessor:

1. To specify the CCSID of the COBOL application source code, use the CODEPAGE compiler option. ¹
   For example, both of the following JCL EXEC statements for COBOL compile jobs specify a CCSID of 37:

   //COB  EXEC  PGM=IGYCRCTL,PARM='...,SQL,CODEPAGE(037),...

   //COB EXEC PGM=IGYCRCTL,PARM='...,SQL,CP(37),...

   Otherwise, if you do not specify the CODEPAGE compiler option, the default COBOL compiler CCSID is passed to the Db2 coprocessor and is used as the CCSID for the source code. The default COBOL compiler CCSID is 1140 unless you changed it.

   The following JCL EXEC statement for a COBOL compile job does not explicitly specify a CCSID. In this case, the COBOL compiler passes the default CCSID, 1140, to the Db2 coprocessor.

   //COB EXEC PGM=IGYCRCTR,PARM='...,SQL(),...'

   CCSID 1140 is the equivalent to CCSID 37 plus the euro symbol (€). However, be aware that conversions, and thus conversion cost, still occur between CCSID 1140 and CCSID 37.

   Recommendation: If you are using the Db2 coprocessor on a COBOL application, do not specify the SQL compiler option with the CCSID suboption. If you specify it anyway, and it conflicts with the CODEPAGE compiler value, Db2 issues a warning. ² For example, the following EXEC statement for a COBOL compile job specifies a CCSID value of 1140; the CCSID value 37 is ignored:

   //COB EXEC PGM=IGYCRCTR,PARM='CP(1140),SQL("CCSID(37)")'

   To verify which CCSID value was used, look at the compiler listing and check the CCSID option.

2. To specify whether Db2 or the COBOL compiler determines the CCSID of application data for host variables and parameter markers in the program, specify one of the following compiler options:

   NOSQLCCSID (Recommended option)

   Specifies that the CCSID that is passed from the COBOL compiler is used only for the COBOL application source and string literals. That CCSID is not used for the host variables and parameter markers in SQL statements. For host variables and parameter markers, Db2 uses the CCSIDs that are specified through Db2 mechanisms, as described in the next step.

   Specifying NOSQLCCSID typically yields better performance, because you can then use a Db2 mechanism to specify the host variable CCSIDs.

   NOSQLCCSID simulates the behavior of the precompiler. Specify this option for existing applications that previously used the Db2 precompiler and now use the Db2 coprocessor. By default, the Db2 coprocessor uses the same CCSID value that is passed from the COBOL CODEPAGE(nnnnn) compiler option for both the source code and data. This behavior is different than the Db2 precompiler, which does not use the CCSID from the COBOL compiler. For applications that use the Db2 precompiler, you specify the CCSID for the data through Db2 mechanisms only. When you specify NOSQLCCSID, Db2 does not use the COBOL CCSID for the application data.

   SQLCCSID (default option)

   Specifies that the Db2 coprocessor is to use the CCSID from the COBOL CODEPAGE(nnnnn) compiler option for your application data. ² The CCSID value is the same one that you specified for your COBOL source code.

3. Optional: If you specified the NOSQLCCSID compiler option, you can specify different encoding schemes for data processed by the program. You can use one or more of the following Db2 approaches to specify CCSID values for the application data³, which is called the application encoding scheme:
   • Use the ENCODING bind option.⁴ This option typically yields the best performance.
   • You can override the CCSID for a particular host variable by using the DECLARE VARIABLE statement with the CCSID option.
   • You can override the CCSID for parameter markers in dynamic SQL by specifying the CURRENT APPLICATION ENCODING SCHEME special register. Db2 uses the value of this special register at the time that the statement is executed.
   • If you use an SQL descriptor to define application data the previous options in this list might not apply if CCSID overrides are defined for host variables and parameter markers in the SQL descriptor (SQLDA).
   
4. If you want to specify a Unicode CCSID for a particular variable, declare it as a PIC N USAGE NATIONAL variable.
   For COBOL PIC N USAGE NATIONAL variables, the Db2 coprocessor always uses the CCSID 1200. You do not need to use a DECLARE VARIABLE statement with the CCSID clause for these variables.