This chapter gives information on the limits this COBOL system places on the size or number of various parameters. It also describes restrictions concerning COBOL syntax and programming areas you should be aware of when creating applications. The COBOL system limits equal or exceed all those listed in the X/Open CAE, COBOL Language (XPG4).
This section lists, by category, the maximum size or number of various parameters used in Micro Focus COBOL. The left-hand column gives the affected parameter, and the right-hand column notes the maximum value allowable in the indicated unit of measure.
There are three levels or categories of limit which must be taken into account for any particular environment: COBOL Compiler limits; COBOL run-time system limits; and external limits.
The COBOL Compiler and the intermediate code that it produces are environment independent. The limits associated with the Compiler are environment independent also and cannot be exceeded in any environment. However, at run time, the operating system or hardware can indirectly affect the design or operation of the COBOL run-time system, thereby imposing limits that are lower than those of the Compiler. In addition, the particular configuration of the operating system or hardware environment might directly impose limits that are lower than those of both the Compiler and the run-time system.
16-bit:
On the 16-bit COBOL system, the maximum length
of command lines is 128 characters. The name of the program being called will
take up some of this,leaving a lower limit for the parameters to be passed to
the program.
32-bit:
On 32-bit COBOL systems the maximum length of
a command line is determined by the operating system.
Note: Some Micro Focus tools do limit the command line length to 128 characters. However, user applications should be able to use the operating system limit.
The COBOL Compiler and the intermediate code that it produces are environment independent. The limits associated with the Compiler are environment independent also and cannot be exceeded in any environment. Use this table of limits in conjunction with the later two tables of run time and operating system dependent limits which might well be lower than those of the Compiler.
For limits on files and records and their sizes, see your Programmer's Guide to File Handling.
| Per file (including split-key components) | 255 keys |
| Length of any one key, including split-key | 1016 bytes (performance best below 512) |
| Number of components in a split key | 62 |
|
Number of alternate keys (using COBOL syntax) (with Extfh interface) |
252 252 |
| Alphanumeric literals | 160 bytes |
| PICTURE character string | 30 characters |
| PICTURE replication (for example, n in PIC X(n)) | 256,000,000 |
| Program-ID name | 30 characters |
| Entry point names | 30 characters |
| Programmer defined words | 30 characters |
| External filenames (for program source and object files, copyfiles, data files) | 100 characters (see the section Filenames later in this chapter) |
| Dynamically loadable program names | 100 characters or your system limit, whichever is the smaller. The first 30 characters must be unique. |
| CALL statement | 255 |
| PROCEDURE DIVISION header | 255 |
| ENTRY statement | 255 |
| Total | No limit |
| Data Division | 256 Mbytes |
| Procedure Division | 816 Mbytes
16-bit: |
| COBOL segment | 16 Mbytes |
| Records in a file (all file types) | No limit |
| Actual fixed format line | 80 bytes |
| Effective fixed format line | 72 bytes |
| Free format line | 160 bytes |
| Number of USE GLOBAL AFTER statements in program | 20 |
Depending on the operating system or the hardware on which your COBOL application runs, the design and operational limitations of the COBOL run-time system might be lower than those of the Compiler. These limits, which are listed below, should be used in conjunction with any operating system limits.
For limits on files and records and their sizes, see your Programmer's Guide to File Handling.
| IFs (compiled code only) | 255 |
| PERFORMs | At least 22 See the section PERFORM Nesting |
| CALLs | No specifiable run-time system limit. However, this is limited by the stack space allocated by the operating system. |
| DOS, Windows and OS/2: At program run time |
|
||||
| 32-bit: At program run time and animation time |
Configurable on 32-bit COBOL systems via COBCONFIG tunable |
The operating system or hardware configurations and parameter settings directly impose limits on your COBOL application. You need to check your operating system and hardware to determine the actual values for any limits, but the following items might be affected:
| CALL nesting | Limited by stack space allocated by operating system |
| Total data and procedure size | Limited by available free memory |
| Simultaneously loaded subprograms | Number might be limited by available free memory |
| Environment variables | Limited to a maximum of 64 Kilobytes (or the machine's free space, whichever is smaller) of written environment variables at any one time during the run of an application. |
For operating system limits on files and records, see your Programmer's Guide to File Handling.
16-bit on DOS:
The maximum core heap size on the
16-bit COBOL systems for DOS is:
16-bit on Windows and OS/2:
The maximum core heap size
on the 16-bit COBOL systems for Windows and OS/2 is:
32-bit:
On the 32-bit COBOL systems the maximum core
heap size is limited only by disk space.
This section gives details of items of COBOL syntax that are not implemented, areas of programming you should use with care, and programming restrictions.
The following COBOL syntax documented in the Language Reference is not supported:
Neither of these items is defined in the ANSI standard.
The following OS/VS COBOL syntax is not supported:
This section describes areas of programming that you should avoid or use with care. Unpredictable results might occur when using the following items.
16-bit:
On the 16-bit COBOL system, the implementation
of CHAIN in Micro Focus COBOL might cause " memory full" errors to occur when chaining between
programs linked with the static-linked run-time system. The initial program of
a set is always retained in memory because it contains the global data used by
the run-time system. Hence, if the initial program is large, and the program to
be chained to is large, there might be insufficient memory.
To avoid the problem, if your system uses CHAIN, create a dummy initial program which simply chains to the first real program in the system. If any of the programs chained to are in separate executable files, the dummy program should also be in its own executable file.
Entry points defined using the ENTRY statement can only be accessed after the main entry point (identified by the program-ID) has been called, unless the program is statically linked.
A nested program cannot contain ENTRY statements.
An entry point is an alternative route into a program; an entry point is not treated as a separate program. For more details on entry points, see the chapterWriting Programs, and for UNIX users also the The COBOL Interfacing Environment, both in your Object COBOL User's Guide.
16-bit Windows and OS/2:
On 16-bit Windows and OS/2,
the basename of the .dll file is restricted to a maximum of eight
characters.
A file is identified within a COBOL program by a filename, a user-defined word. Outside the COBOL system it is identified by a filename which must be in an external, operating-system format. DOS, Windows, and OS/2 use the same format; UNIX uses a similar but different format. The DOS format recognizes four components: a drive, a path, a base-name and an extension. The UNIX format recognizes two components: a path and a name.
Micro Focus COBOL imposes a limit of 100 characters on the size of an external filename. COBOL imposes no other limits, but in order for the operating system to handle the filename correctly, any operating system limits must be observed at run time. Some operating systems allow filenames to exceed 100 characters, but such filenames cannot be directly used by a COBOL application.
In the UNIX environment, it is often found convenient to adopt a convention for constructing names for files that simulates the DOS base-name and extension format. It is a convention that a COBOL application can use or ignore. The utilities of the COBOL system use such a convention when they run, and the library routines CBL_SPLIT_FILENAME and CBL_JOIN_FILENAME also support the convention which has been designed to ease portability of applications between DOS, Windows, OS/2 and UNIX (see the chapter Library Routines (Call-by-name) for details). The convention splits a filename into three components: a path, a base-name and an extension.
16-bit:
For the DOS file format used by the 16-bit
COBOL system, the path is considered to include the drive. The limits assumed
by the convention are:
and 8 characters for the base-name and 3 characters for the extension.
32-bit:
For the file format used by the 32-bit COBOL
system for UNIX, Windows NT and OS/2 V2, the limits are 100
characters for the path, 100 characters for the base-name and 100 characters
for the extension.
These COBOL limits will be subject to any lower operating system limits that may be in effect. See your operating system documentation for details.
DOS, Windows and OS/2:
Floating-point literals must
have values between 0.54E-78 and 0.72E+76. See the section Numeric
Literals in the chapter Concepts of the COBOL Language, in your
Language Reference .
The maximum size of the Local-Storage Section is platform specific. To ensure good performance and efficiency we recommend you keep the size to an absolute minimum.
A nested program cannot have a Local-Storage Section.
16-bit:
Because of the mechanism used for controlling
the nesting of PERFORM statements, the maximum nesting of PERFORMs is variable
according to the following rules:
By default, the PERFORM stack is 2048 bytes in size for the static linked run-time system, and 8192 bytes for the shared run-time system, although this is configurable at link time or at run time. See the section Linker Options in the chapter Linking and Library Management on the 16-bit COBOL System.
The depth of PERFORM nesting applies to a whole called suite of
programs; any PERFORMs active at a CALL remain active. Each call requires
142+4p+2q+d bytes on the PERFORM stack, where:
p |
The number of parameters |
q |
The number of 64K segments required to hold the program's Data Division |
d |
The size of any Local-Storage Section rounded up to a multiple of 2. |
32-bit:
The maximum number of levels for standard
PERFORM nestings in a 32-bit COBOL system is 100 in .int code. The
maximum for .gnt code depends on the amount of memory allocated by your
operating system environment.
All environments:
The maximum level of PERFORM nesting when animating is 254. If your
program exceeds this level, then Animator will only Step, even if Zoom mode is
specified.
16-bit:
On the 16-bit COBOL system, the theoretical
maximum size for a program is 256Mb for data, and 4096Mb for code.
On the 16-bit COBOL system, programs created with linked systems may have a smaller maximum size. The maximum size of a single program achievable with linked systems is limited by the maximum of 255 segments in an .obj file. With Micro Focus COBOL, standard segment usage limits this to 242 user segments, each being up to 64K in size, and each containing either code or data. Hence, a single linked program can contain no more than 15Mb of data. In practice, the size of code and data in a program is further restricted by the amount of memory available. Within these guidelines, there are the following restrictions:
UNIX:
Each named procedure within an object program
requires a relocation entry in an executable file. When building an executable
COBOL application, there will be at least one named procedure in the COBOL
object program, plus many more in the COBOL system libraries. Additional object
programs held in .o files or within .a library files can be
specified to the cob command in order to build an executable file and will
contain many more procedure-names. In cases where many object files are linked
together, the number of procedure-names might exceed the limit of the system
linker.
The maximum number of relocation entries in a COFF object is operating system dependent. In practice, this usually limits the number of relocation entries for code or for data to 65535.
If you exceed this limit, the system linker returns an error message or quits, returning an error code to the shell. The number of names that could cause an error is operating system dependent, and the error message returned depends on how the operating system detects the overflow.
With Micro Focus COBOL, there are two ways in which you can avoid this limit to relocation entries:
16-bit and UNIX:
On the 16-bit and UNIX COBOL systems, the maximum number of data entries
a screen can contain is 200. This can be any combination of fields or groups.
If you attempt to use more than 200 entries on a screen the following message
appears:
Field table full
and the results on the existing fields are undefined. You should, however, use groups to avoid using this many entries and to make the generated code smaller and easier to maintain.
According to the ANSI standard, numbers are limited to 18 significant decimal digits. All significant digits must be within 18 digits of the decimal point.
Micro Focus COBOL gives an ON SIZE ERROR if either of the following conditions occur:
16-bit:
On
the 16-bit COBOL system, to allow a segmented program to call another segmented
program, the called program must be compiled with the NOREALOVL directive, and
linked using the resulting .lnk
response file.
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