Storage Initialization

[Kurt Goolsbee <K.goolsbee@xxxxxxxxxxxxx>]

We have an MI application that does user defined screen IO.  The UFCB
definition looks like this:

DCL DD UFCB CHAR(214) BDRY(16);                                             
    DCL SPCPTR .ODP           DEF(UFCB) POS(  1);                           
    DCL SPCPTR .INBUF         DEF(UFCB) POS( 17);                           
    DCL SPCPTR .OUTBUF        DEF(UFCB) POS( 33);                           
    DCL SPCPTR .OPEN-FEEDBACK DEF(UFCB) POS( 49);                           
    DCL SPCPTR .IO-FEEDBACK   DEF(UFCB) POS( 65);                           
    DCL SPCPTR .NEXT-UFCB     DEF(UFCB) POS( 81);

    DCL DD *         CHAR(32) DEF(UFCB) POS( 97);/* RESERVED */             
    DCL DD FILE-NAME CHAR(10) DEF(UFCB) POS(129) INIT("PMSCREEN");          
    DCL DD LIB-ID    BIN ( 2) DEF(UFCB) POS(139) INIT(-72);                 
    DCL DD LIBRARY   CHAR(10) DEF(UFCB) POS(141) INIT("*LIBL");             
    DCL DD MBR-ID    BIN ( 2) DEF(UFCB) POS(151) INIT(-73);                 
    DCL DD MEMBER    CHAR(10) DEF(UFCB) POS(153) INIT("*FIRST");
/*  LIB-ID AND MBR-ID ARE NEGATIVE TO SIGNIFY THAT NO LIBRARY */        
/*  AND MEMBER ARE SPECIFIED.                                 */

    DCL DD ODP-DEV-NAME       CHAR(10) DEF(UFCB) POS(163);              
    DCL DD ODP-DEV-INDEX      BIN ( 2) DEF(UFCB) POS(173);
    DCL DD FLAGS-1            CHAR( 1) DEF(UFCB) POS(175) INIT(X'80');  
    DCL DD FLAGS-2            CHAR( 1) DEF(UFCB) POS(176) INIT(X'00');

    DCL DD REL-VERSION        CHAR( 4) DEF(UFCB) POS(177) INIT("0100");   
    DCL DD INVOC-MARK-CNT     BIN ( 4) DEF(UFCB) POS(181);                
    DCL DD MORE-FLAGS         CHAR( 1) DEF(UFCB) POS(185) INIT(X'04');    
    DCL DD TAPE-END-OPTION    CHAR( 1) DEF(UFCB) POS(186);
    DCL DD *                  CHAR(22) DEF(UFCB) POS(187);

    /*  RECORD PARAMETER */                                              
    DCL DD RECORD-PARAM       BIN ( 2) DEF(UFCB) POS(209) INIT(1);       
    DCL DD RECORD-LENGTH      BIN ( 2) DEF(UFCB) POS(211) INIT(5000);

    DCL DD NO-MORE-PARAMS     BIN ( 2) DEF(UFCB) POS(213) INIT(32767);


Occasionally we get an open failure for the display file and a big dump.
Nine times out of ten the SEPT gets corrupted and we have to use SST to go
fix it.  The corruption is always in the same place.  


DUMP TAKEN FOR UNMONITORED ESCAPE MESSAGE

.MESSAGE ID-                   CPF4182

.MESSAGE FILE-                 QCPFMSG                LIBRARY-
*LIBL                                              
.SEVERITY-                     50

.MSGTYPE-                      0F

.SENDING-

..PROGRAM-                     QDMCOPEN

LIBRARY-                       QSYS

..INSTRUCTION-                 15D0

.RECEIVING-

..PROGRAM-                     PM0002V                LIBRARY-
PSSECURE                                           
..INSTRUCTION-                 0003

.MESSAGE-

  File PMSCREEN in library *LIBL member or device *N not opened.

.MESSAGE DATA-

  000000 D7D4E2C3 D9C5C5D5 4040D7D4 E2C3D9C5 C5D54040 5CD3C9C2 D3404040
40405CD5 *PMSCREEN  PMSCREEN  *LIBL     *N*   
  000020 40404040 40404040 5CD54040 40404040 40400050 D6000000 00000000
00000000 *        *N         &O           *   
  000040 80000000 00000000 D426DC45 340050A0 80000000 00000000 D426DC45
340050A0 *        M üá  &µ        M üá  &µ*   


Offset X'0060' in QINSEPT is the F.U. entry.
.POINTERS-

  000000   SYP 02 01 QT3REQIO                        04 01 QSYS
3F10  0000  *PGM     
  000010   SYP 02 01 QWSCLOSE                        04 01 QSYS
3F10  0000  *PGM     
  000020   SYP 02 01 QSFGET                          04 01 QSYS
3F10  0000  *PGM     
  000030   SYP 02 01 QWSOPEN                         04 01 QSYS
3F10  0000  *PGM     
  000040   SYP 02 01 QWSPBDVR                        04 01 QSYS
3F10  0000  *PGM     
  000050   SYP 02 01 QWSRST                          04 01 QSYS
3F10  0000  *PGM     
  000060   SPP 1A EF QPADEV0013TCHRI     484419
00004EA0  8000       
  000070   SYP 02 01 QSFCRT                          04 01 QSYS
3F10  0000  *PGM     
  000080   SYP 02 01 QWSSPEND                        04 01 QSYS
3F10  0000  *PGM     
  000090   SYP 02 01 QDCVRX                          04 01 QSYS
3F10  0000  *PGM

Now for the questions.  

Is the UFCB properly initialized?  The way I interpret the S/38 Data Area
manual is that the ODP and the NEXT-UFCB pointers should be initialized to
NULL.  Can you rely on these being set to NULL the first time a program is
called?  The problem seems to appear mostly toward the end of the day.

The S/38 Data Areas manual also indicates that FLAGS-2 should be X'30' to
indicate that we want to be open for reading and writing.  Is this
necessary?  Other examples ( Leif's book @ http://iseries400.org
<http://iseries400.org>  ) initialize this byte to X'00'.  

Regards,

Kurt Goolsbee

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