S 4.218 Information on character set conversion in z/OS systems

Initiation responsibility: Head of IT

Implementation responsibility: Application Developer, Administrator

The z/OS system normally works with the EBCDIC character set (Extended Binary Coded Decimal Interchange Code). This applies both to the MVS files (Multiple Virtual Storage) and to the HFS files (Hierarchical File System). Exceptions are only possible in the zFS file system. Windows and Unix systems mostly work with the ASCII character set (American Standard Code for Information Interchange). The following rules must be taken into consideration regarding the communication between the different systems:

• If text files are to be transmitted, conversion tables must be used performing character set conversion. These tables are supplied together with the z/OS system. However, care must be taken to use the correct table.
• During binary data transmission, it must be ensured that the conversion function is disabled, since the data will be useless otherwise.
• When transferring data from Unix or Windows systems to an HFS (Hierarchical File System) of the z/OS system - and vice versa - using FTP (File Transfer Protocol), it must be observed that the proper conversion option is activated during transfer.
• Specifically when transmitting program source code, it must be checked that all characters (specifically some special characters) really are compiled properly so that undetected program errors caused by conversion can be ruled out. For example, incorrect characters in constant definitions do not result in a compiler error in some cases, but may possibly only be detected very much later during execution.

Review questions:

• Is importance attached to performance of the character set conversion which may be required when transmitting text files between z/OS systems and other systems?
• If character set conversion is required for data exchange with z/OS systems: Is the proper conversion table used in each case?
• Is it ensured when transmitting binary data between z/OS systems and other systems that the character set conversion is switched off?
• Is it ensured when transferring data between z/OS systems and other systems using FTP that the proper conversion option is enabled during transfer in each case?
• Is it checked when transmitting program source code between z/OS systems and other systems that all characters are compiled properly?