Optimizer Options

When the Natural Optimizer has been activated, you can specify checks by setting the options explained in this section.

The options cannot be used for specifying statements to be optimized.

This document covers the following topics:

List of Options

The following table lists and describes the Natural Optimizer Compiler options. Default values are underlined (this is the value that will be assumed if the option is not present).

A Natural Optimizer Compiler option consists of a string surrounded by brackets or single quotation marks (except in the Natural OPTIONS statement), with options separated by commas. Some options have values, while the very existence of some options in the option string is sufficient to modify the environment.

The following rules apply:

  • Optional clauses are surrounded by square brackets [ ].

  • Choices are surrounded by curly braces { }.

  • Each choice is separated by vertical lines "|".

  • Only one of these choices can be specified;

    ON is equivalent to Y (Yes),

    OFF to N (No).

  • Options specified without the optional clause ON or OFF (if applicable), or their equivalent values, are interpreted as set to ON. For example, OVFLW is identical to OVFLW=ON.

  • Except for the option OFF, any specified option switches on optimizing (as if ON was specified) and the default values apply. For example, INDEX is identical to ON,INDEX.

Option Explanation
ABEND Forces the Natural Optimizer Compiler to generate code which causes Natural to be abnormally terminated immediately when the ABEND option is encountered by the Natural Optimizer Compiler during compilation. The option must appear by itself or it will be ignored. Other parameters are not changed or reset by this option. This option can be useful for debugging purposes.
CACHE[={ON| OFF |Y|N}] Switches variable caching on or off. See also Variable Caching in the section Performance Considerations.
CPU= /370 Specifies the target architecture.
DIGTCHCK[={ON| OFF |Y|N}] Specifies whether the digits of packed and unpacked numeric fields (formats P and N) are to be checked when moving to another variable of the same type and precision. For example, if DIGTCHCK is ON and an unpacked numeric variable (format N) contains an invalid digit, such as X'FA', moving to another unpacked numeric variable with the same precision will generate a S0C7 (or NAT0954) error. If DIGTCHCK is OFF, no error is generated but the generated code is much faster.
ERRDUMP[={ON| OFF |Y|N}] Specifies whether NOC should abend if an error condition is detected during the compile phase. This is useful for debugging the Natural Optimizer Compiler itself.
INDEX[={ON| OFF |Y|N}] Specifies whether array indexes will be checked for out-of-bound values in the optimized code.

See also the following Note.

INDX[={ON| OFF |Y|N}] Specifies whether array indexes will be checked for out-of-bound values in the optimized code.

Additionally, RANGE will be set on. Therefore, this option is equivalent to INDEX=ON,RANGE=ON.

See also the following Note.

IO[={ON| OFF|Y|N}] Provided for compatibility reasons only. No effect.
LOOPS[={ON| OFF |Y|N}] Provided for compatibility reasons only. No effect.
MIX[={ON| OFF |Y|N}] Provided for compatibility reasons only. No effect.
NODBG[={ON| OFF|Y|N}] If NODBG=OFF/N (default), the Natural Debugger can be used to debug optimized code (then, additional code is generated to check whether TEST mode has been set on).

If NODBG=ON/Y, less code will be generated, the program will run faster and consume less CPU time. On the other hand, the functionality of the Natural Debugger will be limited, because the Natural Debugger might not receive control for optimized statements.

See also NODBG in the section Performance Considerations.

NOSGNTR[={ON| OFF |Y|N}] Applies to packed numbers only.

If NOSGNTR=OFF (default), signs of positive packed numbers which are the result of an arithmetic operation or the target of an assignment are set according to the COMPOPT parameter PSIGNF. If NOSGNTR=ON, the signs resulting from execution of the generated machine instruction are left unchanged. See also the section Influence of other Natural Parameters.

ON Switches on optimizing. If no additional option is specified, the default value defined for each option is in effect. As indicated in the following Note, this may cause unintended results, in particular regarding the options INDEX, INDX, OVFLW, and RANGE.
OFF Switches off optimizing.
OPTLEV={ 2|3} Specifies optimization level - roughly equivalent to the number of passes through the program.

OPTLEV=3 is useful when PGEN is specified, since some branch targets cannot be determined during the first pass and PGEN output is made during the last pass. Thus, some values may be shown improperly.

OVFLW[={ON| OFF |Y|N}] Specifies whether checks for overflow in arithmetic operations or assignments will be included in the optimized code.

See also the following Note.

PGEN[={ON| OFF |Y|N}] Specifies whether a disassembly of the optimized code should be output. This option also enables all other tracing options: see PGEN Option in the following section.
RANGE[={ON| OFF |Y|N}] Specifies whether range checks will be performed in operations with arrays. This ensures that array ranges will have an equal number of elements in corresponding dimensions of all operands.

See also the following Note.

SIGNCHCK[={ ON|OFF|Y|N}] Specifies whether the result of a multiplication with a packed or unpacked numeric multiplier should be checked for a negative zero. If zero is multiplied by a negative number, the MP machine instruction generates a negative zero result. If SIGNCHCK is on, this negative zero is converted to a positive zero. The check for a negative zero is done for every multiplication with a packed or unpacked numeric multiplier.
TRENTRY For internal use by Software AG only. Do not change the setting of this parameter.
ZD[={ ON|OFF|Y|N}] Specifies whether divisors should be checked for zero. If this option is specified, then code is inserted, so that the program behaves according to the ZD profile parameter of Natural, that is, Natural error NAT1302 is issued or the result is zero. If this option is not specified, Natural error NAT0954 occurs if the divisor is zero.

See also ZD - Zero-Division Check in the Natural Parameter Reference documentation.


If the option INDEX, INDX, OVFLW or RANGE is set, extra instructions are added to the generated code to detect data overflow and index-out-of-range situations should they occur during program execution. Although the use of these options slightly increases the generated code, we recommend to use them to guarantee that erroneous programs are detected and cannot lead to unpredictable results, storage corruptions or abnormal program terminations.

Below is information on:

Example of INDEX and OVFLW

1 P1 (P1/9)
1 P3 (P3/9)
1 I (I4)
1 J (I4)
1 K (I4)
1 L (I4) 
P1(I:J) := P3(K:L)

Explanation of Example

With INDX=ON or INDEX=ON set, code is generated to verify that I, J, K and L are within the ranges defined for P1 and P3 respectively.

With INDX=ON or RANGE=ON set, code is generated to verify that I:J and K:L denote ranges of the same length.

With OVFLW=ON set, code is generated to verify that the value of P3 fits into the corresponding P1 variable.

For example: Value 100 would cause an overflow here.

Example Error Situation:

If one of the occurrences of P3 contains the value 100, with OVFLW=OFF set, the value assigned to the corresponding P1 occurrence will be zero. If the index variable I is zero or greater than 9, with INDX=OFF set, storage areas that do not belong to Array P1 will be corrupted. If these options (OVFLW and INDX) are set to ON, a Natural error occurs like it does in standard Natural runtime.

For the NOC option specified above, additional code is generated. However, this is well compensated for by the advantage of a check that, for example, protects against hard-to-debug errors. Undetected errors can, of course, lead to unpredictable results.

Optimum Code Generation

To assure that the least amount of code is generated and thus achieve optimum performance, use:


However, only apply this setting to objects that have been thoroughly debugged; see also Note for INDEX, INDX, OVFLW and RANGE.

PGEN Option

The PGEN option causes the Natural Optimizer Compiler to output the generated code and internal Natural structures. Thus, code and structures can be examined, for example, for bug fixing, performance review and support issues.

An understanding of IBM's /370 assembler is required to interpret the results produced by the PGEN option.

We recommend that you use this option with the assistance of your local Software AG representative.

Below is information on:

Setting PGEN

To use the PGEN facility, set the PGEN option when activating on the Optimizer Compiler.

Since the buffer is kept in memory, it is possible that the user thread will not be big enough to hold the trace information. In this case, try setting PGEN on only for the portion of the program which is to be traced, for example:

Turns tracing on, including tracing of the GPT entries
Turns tracing off

Various options affect the content of the output. The basic PGEN option causes a formatted listing of Natural source lines and a disassembly of the corresponding code to be generated and kept in memory for extraction by the NOCSHOW utility as described below, under Output of the PGEN Option.

The TRSTMT, TRGPT, TRMPT and TRVDT options cause hex dumps of internal data structures associated with each line to be output.

The TRBASES and TRCACHE options cause information on base registers and cache variables to be printed out. 

Sub-Options of the PGEN Option

The following table describes the options when PGEN=ON. For an explanation of the syntax used see the introduction to List of Options above.

Option Explanation
LPP={5|..| 55 |..|255} Lines-per-page for the trace output, only used when TREXT=ON.
NOsrcE[={ON| OFF |Y|N}] If NOsrcE=OFF, the Natural source statement is included in the output.
TRACELEV={ 0 |..|255} Specifies the trace level. Each bit in this one byte value specifies a buffer type to trace; these bits can be set on by using the TRxxx options as well.
TRBASES[={ON| OFF |Y|N}] Specifies whether base register allocations are traced.
TRCACHE[={ON| OFF|Y|N}] Specifies whether CACHE entries are traced.
TREXT[={ON| OFF |Y|N}] If TREXT=ON, trace is directed to the user exit NOCPRINT as described below.
TRGPT[={ON| OFF |Y|N}] Specifies whether GPT entries are traced.
TRMPT[=ON| OFF |Y|N}] Specifies whether MPT entries are traced.
TRSTMT[={ON| OFF |Y|N}] Specifies whether STMT entries are traced.
TRVDT[={ON| OFF |Y|N}] Specifies whether VDT entries are traced.

See also the examples below.

Output of the PGEN Option

There are two places to where the Natural Optimizer Compiler can direct the output of PGEN:

Internal Buffer

The contents of this buffer is overwritten each time a CHECK, CAT, STOW or RUN command is executed. A system utility NOCSHOW is provided whereby the contents of this buffer can be viewed, searched or printed.

Start of instruction setTo invoke the NOCSHOW utility

  • Enter the direct command NOCSHOW after a CHECK, STOW, CAT or RUN where the Natural Optimizer Compiler has been active. 

The following PF keys are available on the screen:

Key Function
PF2 Position to top of output
PF4 Position one line backward
PF5 Position one line forward
PF6 Print to report (1)
PF7 Position one page backward
PF8 Position  one page forward
PF9 Print via Entire Connection to report (7)
PF10 Scan for text string
PF11 Repeat scan


If TREXT=ON is specified, the Natural Optimizer Compiler passes every output line to the user exit NOCPRINT instead of adding it to the trace buffer.

NOCPRINT is invoked following normal OS register conventions. Register 1 points to a full word containing the address of the 81 byte print line with ANSI carriage control characters in position 1. Register 13 points to an area of 18*4 bytes which may be used as a save area. Register 14 contains the return address and Register 15 contains the entry address of NOCPRINT.

The user exit NOCPRINT can be written in any language which supports the register conventions described above. It must be linked to the Natural nucleus together with the Natural Optimizer Compiler nucleus.

Working with the PGEN Output

This section provides hints and explanations on how to interpret the output created with the PGEN option.

  • At the top of the PGEN output are some disassembled lines which do not appear to belong to any source line. These are the instructions which make up the prologue, which is executed whenever control passes from non-optimized to optimized code. Permanent base registers are loaded and control is passed to the correct point in the prologue. See Example Section A below.

  • Sometimes a lot of source lines are printed without any code. This indicates that there was no code required or that these statements are excluded from the NOC optimization. See Example Section B below.

    Moreover, when the code generated for a Natural statement consists only of:

    BAS   R14,RETH                           
    DC    X'....'

    this indicates a return back to the standard runtime, as this statement could not be NOC optimized (see line 0170).

  • If the NODBG=OFF (default) has been specified, a sequence of instructions is generated at the start of each Natural statement:

    BALR R9,R11
    DC X'....'

    This sequence sets the line number (in case of error) and checks whether the TEST mode is switched ON. Without this sequence, debugging of NOC-compiled statements by the Natural Debugger is not possible. See Example Section C below.

  • Sometimes there is a line break between disassembled lines. This break indicates an internal statement separation. It happens because often a single Natural statement will generate multiple internal (pseudo-code) statements.

  • The Natural variables operated are inserted in the Assembler code.

  • The items on the right side (e.g. “START 8FEC”) are of internal nature. They document the path how the code was generated by the NOC modules.

  • All kind of addresses inside the code are resolved and provided in the form “=(00044)”. It documents the offset in the code to which the branch is executed.

  • The first and the last code instruction contains the NOC version used to compile this program. The meaning of “4700 8410” is NOC V841.

Example Section A:

 000000 4700 8410           NOP   1040(,R8)                         START  8FEC
 000004 5880 D354           L     R8,CONST                                 D9DC
 000008 5870 D370           L     R7,LOCAL                                 D9DC
 00000C 4810 6006           LH    R1,6(,R6)                                90A0
 000010 1F60                SLR   R6,R0                                    90BA
 000012 47F1 A000           B     0(R1,R10)                                90C0
 000016 4DE0 B040           BAS   R14,RETH                           RETN  F0AA
 00001A 0034                DC    X'0034'                                  F0C0

Example Section B:

  0030 1 I(I4)
  0040 1 P(P7.2)
  0050 1 T(P7.2)
  0070 *
  0080 SETTIME
  0090 *                                                                         

Example Section C:

 0100 FOR I=1 TO 100000                                                                                                                                  

 00001C 0D9B                BASR  R9,R11                             MOVE 1724A
 00001E 004A                DC    X'004A'                                 17278
 000020 D203 7000 8148      MVC   I(4),#KST0148                            97D2
 000026 47F0 A044           B     68(,R10)         =(00044)          GOTO  EF44
 00002A 0D9B                BASR  R9,R11                              ADD 1724A
 00002C 006A                DC    X'006A'                                 17278
 00002E BF0F 7000           ICM   R0,B'1111',I                             BB20
 000032 5A00 8148           A     R0,#KST0148                              1E4E
 000036 0D90                BASR  R9,0                                     F12A
 000038 4710 B15C           BO    NAT1301                                  1E9E
 00003C BE0F 7000           STCM  R0,B'1111',I                             A9CC
 000040 0D9B                BASR  R9,R11                               IF 1724A
 000042 007C                DC    X'007C'                                 17278
 000044 BF0F 7000           ICM   R0,B'1111',I                             BB20
 000048 5900 819B           C     R0,#KST019B                              3FDA
 00004C 47D0 A054           BNH   84(,R10)         =(00054)                EF44
 000050 47F0 A078           B     120(,R10)        =(00078)          GOTO  EF44                                                                              

 0110   ADD 1.00 TO P                                                         
 000054 0D9B                BASR  R9,R11                              ADD 1724A
 000056 0092                DC    X'0092'                                 17278
 000058 FA41 7004 819F      AP    P(5),#KST019F(2)                         20A0
 00005E 0D90                BASR  R9,0                                     F12A
 000060 4710 B15C           BO    NAT1301                                 1071C
 000064 910D 7008           TM    P+4,X'0D'                               120B0
 000068 4710 A070           BO    112(,R10)        =(00070)               120F6
 00006C 960F 7008           OI    P+4,X'0F'                               1210ª
 0120 END-FOR                                                                 
 0130 *                                                                       
 000070 0D9B                BASR  R9,R11                             GOTO 1724A
 000072 00A4                DC    X'00A4'                                 17278
 000074 47F0 A02A           B     42(,R10)         =(0002A)                EF44                                                                              

 0140 T:=*TIMD(0080)                                                          
 000078 0D9B                BASR  R9,R11                             SYFU 1724A
 00007A 00AE                DC    X'00AE'                                 17278
 00007C 4DE0 B0D8           BAS   R14,SYSFUNC                              5F1A
 000080 0190 B881           DC    X'0190B881'                              5F28
 000084 F246 7009 8190      PACK  T(5),#KST0190(7)                   MOVE  AD18
 00008A 910F 700D           TM    T+4,X'0F'                               12130
 00008E 4710 A0A0           BO    160(,R10)        =(000A0)               12176
 000092 17EE                XR    R14,R14                                 1218E
 000094 43E0 700D           IC    R14,T+4                                 12194
 000098 43EE B488           IC    R14,PSGNTR(R14)                         121AA
 00009C 42E0 700D           STC   R14,T+4                                 121B2
 0000A0 F040 7009 0002      SRP   T(5),2,0                                 ACA2
 0000A6 17EE                XR    R14,R14                                 1218E
 0000A8 43E0 700D           IC    R14,T+4                                 12194
 0000AC 43EE B488           IC    R14,PSGNTR(R14)                         121AA
 0000B0 42E0 700D           STC   R14,T+4                                 121B2                                                                              

 0150 T:=T / 10                                                               
 0160 *                                                                       
 0000B4 0D9B                BASR  R9,R11                              DIV 1724A
 0000B6 00C0                DC    X'00C0'                                 17278
 0000B8 F864 D100 7009      ZAP   OP1(7),T(5)                              AC60
 0000BE FD61 D100 81A1      DP    OP1(7),#KST01A1(2)                       327A
 0000C4 F844 7009 D100      ZAP   T(5),OP1(5)                              AC60
 0000CA 910D 700D           TM    T+4,X'0D'                               120B0
 0000CE 4710 A0D6           BO    214(,R10)        =(000D6)               120F6
 0000D2 960F 700D           OI    T+4,X'0F'                               1210A                                                                              

 0170 DISPLAY 'ELAPSED TIME (S)' T                                            
 0000D6 4DE0 B040           BAS   R14,RETH                           RETN  F0AA
 0000DA 00D2                DC    X'00D2'                                  F0C0

 0180 END                                                                     
 0000DC 40D6 D7E3 F844 2000 DC    X'40D6D7E3F8442000'  =' OPT8à..'    END  927E
 0000E4 0000 0000           DC    X'00000000'                                nf
 0000E8 40D5 D6C3 F8F4 F140 DC    X'40D5D6C3F8F4F140'  =' NOC841 '         92E4

Influence of other Natural Parameters

The global parameter ZD influences the behavior of the NOC compiler. See the description of the ZD option as described under List of Options above.

The COMPOPT parameter PSIGNF (see also the system command COMPOPT in the Natural System Commands documentation) influences the behavior by forcing the signs of positive packed decimal numbers to F if ON, and to C if OFF. The parameter is applied if NOSGNTR=OFF is specified.

See the chart below for packed data (Format P) ":"

NOSGNTR=OFF and  PSIGNF=ON All signs are normalized to F (default).
NOSGNTR=OFF and  PSIGNF=OFF All signs are normalized to C.
NOSGNTR=ON   All signs are left as they were generated by the last operation.

For numeric data (Format N) the signs are always normalized to F, regardless of the settings of NOSGNTR and PSIGNF.