System z host data format considerations

The following are considerations, restrictions, and limitations that apply to the use of System z host data internal representation.

The CHAR and FLOAT compiler options determine whether System 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 System z host data format support for COBOL programs that are translated by the separate or integrated CICS translator and run on TXSeries.

Date and time callable services

You can use the date and time callable services with the System z host data format internal representations. All of the parameters passed to the callable services must be in System 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 AIX workstation and the System z host, it is possible if FLOAT(HEX) 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 System 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 System z host data format compiler options can be used with DB2 programs.

Object-oriented syntax for Java interoperability

The System z format of floating-point data items must not be specified for arguments or returning items in INVOKE statements.

Distributed Computing Environment applications

The System 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 COLLSEQ(EBCDIC), CHAR(EBCDIC), and FLOAT(S390) to process EBCDIC character data and hexadecimal floating-point data that is acquired from these files.

SORT

All of the System z host data formats except DBCS (USAGE DISPLAY-1) can be used as sort keys.

related concepts  
Formats for numeric data

related references   
Compiler options