Enterprise COBOL V5/V6 and AMODE RMODE. Tom Ross Captain COBOL April 1, 2016

Transcription

1 Enterprise COBOL V5/V6 and AMODE RMODE Tom Ross Captain COBOL April 1, 2016

2 What are AMODE and RMODE? Attributes of executables AMODE 31, RMODE 24 Program Management Binder options AMODE=31,RMODE=24 HLASM Assembler instructions AMODE 31, RMODE 24 RMODE is also a COBOL compiler option RMODE(24 ANY AUTO) It was added to support NORENT above the line in the 1990s NORENT is no longer supported for above the line loading NORENT programs have RMODE 24 always in COBOL V5 There is no such thing as Compiling with AMODE 31 2

3 How does compiler communicate with the BINDER for AMODE and RMODE? All COBOL compilers set AMODE and RMODE BINDER reads this in Object program format Combines all of the different objects and sets the resulting attribute in Program Object All COBOL compilers set AMODE=31 COBOL compilers V5 and later set AMODE=MIN There is no way to tell the BINDER about RENT Users still have to set REUS manually if they need it From the COBOL Migration Guide: If you compile with the RENT compiler option, you must tell the binder that a module is RENT with REUS=RENT. 3

4 Where does WORKING-STORAGE data go? For NORENT programs, data is in the executable RMODE of executable decides above or below the line For RENT programs, memory is acquired for WORKING- STORAGE and other areas at run time DATA(24) says get data below the line DATA(31) says get it from wherever, which might be above the line, not guaranteed The LE runtime options ALL31 and HEAP ALL31 ALL31(OFF) says that some programs are not AMODE 31 ALL31(ON) says all programs are AMODE 31 HEAP HEAP(,,ANYWHERE) says it is OK to get HEAP above the line HEAP(,,BELOW) says HEAP must be below 4

5 Where does WORKING-STORAGE data go? Examples: RENT program, compiled with DATA(31), run with HEAP(,,BELOW): WORKING-STORAGE and other areas below the line RENT program, compiled with DATA(24), run with HEAP(,,ANYWHERE) WORKING-STORAGE and other areas below the line RENT program, compiled with DATA(31), run with HEAP(,,ANYWHERE) WORKING-STORAGE and other areas acquired from unrestricted storage (could be above the line) 5

6 Where does WORKING-STORAGE data go? For RENT programs, memory is acquired for WORKING- STORAGE and other areas at run time Always from HEAP in Pre-V5 compilers In COBOL V5.1 originally, from WSA, which is a coordinated effort between C/C++, BINDER and COBOL runtime Not a good idea! Too many cases of many large programs bound together Load time was VERY slow Also, STORAGE option no longer worked for initializing 6

7 Where does WORKING-STORAGE data go? COBOL WORKING-STORAGE is allocated from heap storage when the COBOL program is compiled with the RENT option and is in one of the following cases: Compiled with Enterprise COBOL V4.2 or earlier releases Compiled with the DATA(24) compiler option Running in CICS A COBOL V5.1.1 or later program in a program object that contains only COBOL programs (except COBOL 5.1.0) and assembler. There are no Language Environment interlanguage calls within the program object and no COBOL V5.1.0 programs. A COBOL V5 program in a program object where the main entry point is COBOL V5. In this case, the program object can contain Language Environment interlanguage calls, with COBOL statically linking with C, C++ or PL/I. All COBOL V5 programs within such program objects (even if they are not the main entry point) have their WORKING-STORAGE allocated from heap storage. A COBOL V6.1 or later program 7

8 Where does EXTERNAL data go? In addition to affecting how storage is obtained for dynamic data areas (WORKING-STORAGE, FD record areas, and parameter lists), the DATA compiler option can also influence where storage for EXTERNAL data is obtained. Storage required for EXTERNAL data is obtained from unrestricted storage if the following conditions are met: The program is compiled with the DATA(31) and RENT compiler options. The HEAP(,,ANYWHERE) runtime option is in effect. The ALL31(ON) runtime option is in effect. 8

9 Adding New COBOL to Old Apps Example: Mixing new and old (all calls DYNAMIC) NORENT RMODE (ANY) COBOL V3 P1 P1 DATA RENT DATA(31) COBOL V5 P3 RENT DATA(24) COBOL V5 P5 16 MB Line P3 DATA Won't work for P1 DATA or P3 DATA VS COBOL II P2 COBOL V5 P4 ASM P6 AMODE 24 P2DATA P4 DATA P5 DATA P6 DATA NORENT RES NORENT RMODE (AUTO 24)

10 Converting assembler to AMODE 31 More than just link-editing with AMODE=31! Sometimes just changing AMODE 24 to AMODE 31 in source is all you need to do Before you do that, check out the following first Use of the SPM (set program mask) instruction LA instruction used to clear the high-order byte of a register Address fields that are less than 4 bytes Use of the ICM (insert characters under mask) instruction AMODE of subprograms AMODE of CALLing programs S8216TR / 24FEB02

11 Converting assembler to AMODE 31 For a good discussion of 31-bit addressability issues, see the z/os MVS Assembler Services Guide, Chapter 5, "Understanding 31-Bit Addressing. Chapter 5.2 has notes on converting from 24- to 31-bit addressing mode. For 31-bit I/O issues, see DFSMS Macro Instructions for Data Sets Chapter 2, "Non-VSAM Macros" contains information for each macro, regarding 31-bit addressability considerations. Appendix A in Appendix 1.1 contains a table, indicating for each macro, whether it can be issued in 31-bit amode. 0/com.ibm.zos.v2r2.ieaa600/planfor.htm?lang=en S8216TR / 17FEB03

12 Converting assembler to AMODE 31 Use of the SPM (set program mask) instruction Does the module depend on the instruction length code, condition code, or program mask placed in the high order byte of the return address register by a 24-bit mode BAL or BALR instruction? One way to determine some of the dependencies is by checking all uses of the SPM (set program mask) instruction. SPM might indicate places where BAL or BALR were used to save the old program mask, which SPM might then have reset. The IPM (insert program mask) instruction can be used to save the condition code and the program mask. LA instruction used to clear high-order byte of register This practice will not clear the high-order byte in 31-bit addressing mode Use SR and ICM S8216TR / 24FEB02

13 Converting assembler to AMODE 31 Address fields that are less than 4 bytes Are any address fields that are less than 4 bytes still appropriate? Make sure that a load instruction does not pick up a 4-byte field containing a 3-byte address with extraneous data in the high-order byte Make sure that bits 1-7 are zero Use of ICM (insert characters under mask) instruction The use of this instruction is sometimes a problem because it can put data into the high-order byte of a register containing an address, or It can put a 3-byte address into a register without first zeroing the register. If the register is then used as a base, index, or branch address register in 31-bit addressing mode, it might not indicate the proper address S8216TR / 24FEB02

14 Converting assembler to AMODE 31 AMODE of subprograms If AMODE 24 then shared data must be below 16M line AMODE of CALLing programs If AMODE 24, might have to handle mode switching COBOL dynamic CALL handles this for you S8216TR / 24FEB02

15 Converting assembler to AMODE 31 If no issues with previous 6 items: Use of the SPM (set program mask) instruction LA instruction used to clear the high-order byte of a register Address fields that are less than 4 bytes Use of the ICM (insert characters under mask) instruction AMODE of subprograms AMODE of CALLing programs Just add AMODE statement to the source S8216TR / 24FEB02

16 Converting assembler to AMODE 31 ASM2COB CSECT ASM2COB AMODE 31 ASM2COB RMODE ANY * EXTRN COBSUB ============================================ * Save callers regs and chain save areas * ============================================ STM 14,12,12(13) Store incoming registers LR 12,15 Base ASM2COB on Register 12 USING ASM2COB,12 * LA 15,SAVEAREA Get this program's save area ST 13,4(,15) Save caller's save area pointer ST 15,8(,13) Store back this program's save * save area pointer LR 13,15 Load standard save area Register 13 LOAD EP=IGZEDT4,ERRET=NOTFOUND LR 1,0 MVC PGMHDR,6(1) Move in program header WTO MF=(E,WTOMSG) Display program header DELETE EP=IGZEDT4 B SETPLIST * NOTFOUND WTO 'IGZEDT4 was not found',routcde=(11) * S8216TR / 24FEB02