Maintaining a read chain?

[Robert J.M. Edis]

G'day Martyn

First of all, your "RUN SCREEN " is calling a subscreen, not a slave screen.
Slave screens have a MASTER file passed to them, usually the PRIMARY file of
the calling screen.  Remove the 'SLAVE' from the SCREEN statement as this
will automatically associate the subscreen's query transaction with the
calling screen.

By default, PowerHouse with Oracle Rdb generates two transactions per
screen, a query and an update.  The query trasnaction is being inherited by
you subscreen.  The default commit is mode and when this changes on your
subscreen the query transaction is commited.  The result being that when you
get back to the calling screen the query transaction is restarted and your
read chain is broken.

Declare a new QUERY transaction on the subscreen and this should prevent the
calling screen's query transaction from being reset.

It's been a while since I worked with Rdb but I believe this is basically
it.

Regards,

Blue 

-----Original Message-----
From: Thomson, Martyn EDUC:EX
To: 'POWERHOUSE Listserv'
Sent: 3/3/00 1:47 PM
Subject: Maintaining a read chain?

I have a simple one-record screen to maintain a SUSPENSE table. Access
can
be sequential so user can page through the records. Each record has a
list
of error codes, and by entering "ERR"  in the Actionbar a design
procedure
executes a "RUN SCREEN" command, passing the list of codes to a slave
screen
to display error messages from a designer file.
My problem is, when user exits the error screen and returns to the main
screen, the read chain is lost and PageDown just starts over from the
first
record, rather than displaying the next record.  The slave screen must
be
committing the Query transaction. How can I prevent that and retain the
read
chain in the main screen?
I've tried using the TRANSACTION stmt to try to isolate the files in the
two
screens; I've tried declaring the primary file as an aliased secondary,
but
can't find a combination that works.
The Dictionary Transaction Model is Optimistic and dual i.e. Entry/Find
Model: Consistency, Select Model: Concurrency

Here's the relevant code - 

SCREEN TRAX1424 ACTIVITIES FIND, CHANGE, DELETE 
FILE SUSPENSE IN TRAX PRIMARY
ACCESS VIAINDEX KEY_SUSP_MARK_RESP_OCR_NO REQUEST STUD_NO
ACCESS SEQUENTIAL 
...
PROCEDURE DESIGNER ERR
 BEGIN
     RUN SCREEN XTR$EXEC:TRAX233 PASSING T_ERR_CODES MODE F
 END

SCREEN TRAX233 SLAVE RECEIVING T_ERR_CODES
FILE TAB_ERRORS IN TRAX DESIGNER
...
PROCEDURE INITIALIZE
BEGIN
;display first 15 error codes/messages; if more, prompt user to hit
RETURN
for next page
  LET T_REC_CNT=1
  FOR 15
  BEGIN
     GET TAB_ERRORS VIAINDEX ERR_CODE USING T_ERR_CODES[T_REC_CNT * 3
-2:3]
OPT
     IF ACCESSOK
     THEN BEGIN
        LET T_ERR_MSG = ERR_MSG OF TAB_ERRORS
        DISPLAY T_ERR_MSG
     END
     LET T_REC_CNT=T_REC_CNT + 1
  END

Is what I'm trying to do possible? All comments/suggestions welcome.
I'm using 7.10G1 for OpenVMS, and Rdb 7.0
Martyn Thomson
Ministry of Education, BC
 

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