IBM Z host data format considerations

The following information is about considerations, restrictions, and limitations that apply to the use of IBM Z® host data internal representation.

The CHAR and FLOAT compiler options determine whether IBM Z host data format or native data format is used (other than for COMP-5 items or items defined with the NATIVE phrase in the USAGE clause). (The terms host data format and native data format in this information refer to the internal representation of data items.)

CICS access

There is no IBM Z host data format support for COBOL programs that are translated by the separate or integrated CICS® translator and run on TXSeries® or CICS TX.
Note: Effective 9 August 2024, IBM withdraws from marketing IBM CICS TX Standard (5900-ALU) and IBM CICS TX Advanced (5737-K69).

Date and time callable services

You can use the date and time callable services with the IBM Z host data format internal representations. All of the parameters passed to the callable services must be in IBM Z host data format. You cannot mix native and host data internal representations in the same call to a date and time service.

Floating-point overflow exceptions

Due to differences in the limits of floating-point data representations on the Linux® workstation and the IBM Z host, it is possible if FLOAT(BE) is in effect that a floating-point overflow exception could occur during conversion between the two formats. For example, you might receive the following message on the workstation when you run a program that runs successfully on the host:


IWZ053S An overflow occurred on conversion to floating point

To avoid this problem, you must be aware of the maximum floating-point values supported on each platform for the respective data types. The limits are shown in the following table.

Table 1. Maximum floating-point values
Data type Maximum workstation value Maximum IBM Z host value
COMP-1 *(2**128 - 2**4)

(approx.*3.4028E+38)

*(16**63 - 16**57)

(approx.*7.2370E+75)

COMP-2 *(2**1024 - 2**971)

(approx.*1.7977E+308)

*(16**63 - 16**49)

(approx.*7.2370E+75)

* Indicates that the value can be positive or negative.

As shown above, the host can carry a larger COMP-1 value than the workstation and the workstation can carry a larger COMP-2 value than the host.

Db2

The IBM Z host data format compiler options can be used with Db2® programs.

Distributed Computing Environment applications

The IBM Z host data format compiler options should not be used with Distributed Computing Environment programs.

File data

  • EBCDIC data and hexadecimal binary data can be read from and written to any sequential, relative, or indexed files. No automatic conversion takes place.
  • If you are accessing files that contain host data, use the compiler options BINARY(BE), COLLSEQ(EBCDIC), CHAR(EBCDIC), and FLOAT(BE) to process binary data, EBCDIC character data and hexadecimal floating-point data that is acquired from these files.