Negative DBKEYs
Article ID: 37971
Updated On:
Products
Issue/Introduction
Question:
Is it possible to calculate the page number and line index for negative DBKEYs?
Answer:
DBKEYs that exceed x'7FFFFFFF' or 8,388,607 become negative in an S9(8) COMP SYNC field because the high order bit in the left most byte which represent the sign becomes a one.
An assembler program can be called from ADS or a DC or Batch Cobol program to separate the page number from the line index based on the radix.
Other Relevant Information
RECORD FORMAT that should be passed to this program:
01 DBKEY-RECORD.
02 ACCEPTED-DBKEY PIC S9(08) USAGE COMP.
02 DBKEY-PAGE PIC S9(08) USAGE COMP.
02 DBKEY-LINE PIC S9(03) USAGE COMP.
02 RADIX PIC 9(1).
02 DISP-PAGE PIC 9(08).
02 DISP-LINE PIC 9(04).
NOTE: The first three fields MUST be PIC S9(08) USAGE COMP,PIC S9(08) USAGE COMP and PIC S9(03) USAGE COMP.
After control is returned to the COBOL program or dialog :
MOVE W-DBKEY-PAGE TO DISP-PAGE
MOVE W-DBKEY-LINE TO DISP-LINE
Before linking to the program from ADS or Cobol accept the DBKEY into ACCEPTED-DBKEY and update the RADIX with 7 or 8. If the RADIX field is not updated it will default to 8.
Program source for interface with ADS and Cobol using protocols of IDMS-DC and DC-BATCH:
PRINT ON
SPACE 2
COPY #CSADS
EJECT
PRINT ON
PRINT GEN
#MOPT CSECT=DBKPGM,ENV=USER
@MODE MODE=IDMSDC
@INVOKE PROGRAM=DBKPGM
ENTRY DBKEP1
DBKEP1 CSECT
USING DBKEP1,R12
LR R12,R15
USING CSA,R10 ESTABLISH CSA ADDRESSABILITY
USING SYSLST,R1
L R1,0(R1) LOAD OF DBKEY TO R1 (PIC S9(08) COMP)
CLI 10(R1),X'F7' IS THE RADIX 7?
BE RADIX7 YES, OTHERWISE ASSUME RADIX 8
MVC 5(3,R1),0(R1) MVC PAGE NUMBER TO W-DBKEY-PAGE
MVC 9(1,R1),3(R1) MVC LINE NUMBER TO W-DBKEY-LINE
B EXIT
RADIX7 MVC 4(4,R1),0(R1) MOVE DBKEY TO PAGE NUMBER
NI PAGE+3,X'80' ZERO OUT THE 7 BITS FOR THE RADIX
L R3,PAGE LOAD PAGE NUMBER TO R3
SRL R3,7 SHIFT IT 7 BITS TO THE RIGHT
ST R3,PAGE STORE IT BACK TO PAGE
MVC 9(1,R1),3(R1) MOVE THE LINE NUMBER
NI LINE+1,X'7F' ZERO OUT THE FIRST BIT FOR THE PAGE
EXIT #RETURN
# BALI
LTORG
EXIT BR 14
SYSLST DSECT
DBKEY DS F
PAGE DS F
LINE DS H
END
The program should be preprocessed with IDMSDMLA, then assembled and linked with SYSLIN input:
//SYSLIN DD *
INCLUDE DISTLOAD(IDMS)
INCLUDE OBJECT(DBKPGM)
MODE AMODE(31),RMODE(ANY)
ENTRY DBKPGM
NAME DBKPGM(R)
/*
OBJECT is a DDNAME assigned to the link step that receives the DBKPGM object from the assembler step.
Program source for interface with Cobol using protocol of BATCH:
ENTRY DBKPGM
DBKPGM DS 0H
USING DBKPGM,12
USING SYSLST,1
LR 12,15 UPDATE BASE REGISTER
L 1,0(,1) LOAD ADDR OF RECORD TO R1
LA 1,0(1) TURN OFF HIGH ORDER BIT
CLI 10(1),X'F7' IS THE RADIX 7?
BE RADIX7 YES, OTHERWISE ASSUME RADIX 8
MVC 5(3,1),0(1) MVC PAGE NUMBER TO W-DBKEY-PAGE
MVC 9(1,1),3(1) MVC LINE NUMBER TO W-DBKEY-LINE
B EXIT
RADIX7 MVC 4(4,1),0(1) MOVE DBKEY TO PAGE NUMBER
NI PAGE+3,X'80' ZERO OUT THE 7 BITS FOR THE RADIX
L 3,PAGE LOAD PAGE NUMBER TO R3
SRL 3,7 SHIFT IT 7 BITS TO THE RIGHT
ST 3,PAGE STORE IT BACK TO PAGE
MVC 9(1,1),3(1) MOVE THE LINE NUMBER
NI LINE+1,X'7F' ZERO OUT THE FIRST BIT FOR THE PAGE
EXIT BR 14
SYSLST DSECT
DBKEY DS F
PAGE DS F
LINE DS H
END
This program must be linked in with the Cobol program and does not need to be processed by IDMSDMLA.
Additional Information:
CA IDMS Database Administration Guide
Environment
Component:
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