PRB: COM .Dll In MTS 'Sharing' Datasessions Between Instances

   ***************Server Code With Dataenvironment******************
   DEFINE CLASS MTSData AS FORM OLEPUBLIC
      DATAENVIRONMENT=.NULL.
      DATASESSION=2 &&PRIVATE
      PROCEDURE LOAD
         SET DEFAULT TO "c:\MTSTest"
         THIS.DATAENVIRONMENT=CREATEOBJECT("MTSDataEnv")
      ENDPROC
      PROCEDURE movenext
         SKIP 1
      ENDPROC
      PROCEDURE moveprev
         SKIP -1
      ENDPROC
      PROCEDURE movefirst
         GO TOP
      ENDPROC
      PROCEDURE movelast
         GO BOTTOM
      ENDPROC
      PROCEDURE returnrec
         LPARAMETER MyArray
         EXTERNAL ARRAY MyArray
         MyArray(1,1)=fld1
         MyArray(2,1)=fld2
         MyArray(3,1)=fld3
      ENDPROC
   ENDDEFINE

   DEFINE CLASS MTSDataEnv AS DATAENVIRONMENT
      ADD OBJECT cursor1 AS MTScursor
      PROCEDURE INIT
         THIS.OPENTABLES
      ENDPROC
   ENDDEFINE
    DEFINE CLASS MTScursor AS CURSOR
      PROCEDURE INIT
         OPEN DATABASE MTSData SHARED
         THIS.EXCLUSIVE=.F.
         THIS.ALIAS="MTSTest"
         THIS.DATABASE="c:\MTSTest\MTSData.dbc"
         THIS.CURSORSOURCE="MTSTest"
      ENDPROC
   ENDDEFINE
   ****************End Server Code With Dataenvironment**************
				

MORE INFORMATION

NOTE: This happens with any COM server created in Microsoft Visual FoxPro where multiple instantiations of a single object reside in the same process, and the DataSession property is set to 1 - Default Datasession. The variations where this happens are below:

• Multi-Use Local (.exe) COM Server.
• Multi-Use In Process (.dll) Server called twice in one session.
• Multi-Use In Process (.dll) Server in a MTS Package called twice from one session, or once from multiple sessions.

The code in the Steps To Reproduce Behavior section requires a database with a table. You can run the following code to create the database and table:

NOTE: Make sure to change the SET DEFAULT TO line in the SERVER CODE to point to the directory that contains the database.

   CREATE DATABASE MTSData
   CREATE TABLE MTSTest (fld1 c(10) PRIMARY KEY,fld2 N(5,2),fld3 T)
   FOR i=1 TO 4
      INSERT INTO MTSTest VALUES (STR(i),i,DATETIME()+ (i*60))
   ENDFOR
				

Steps to Reproduce Behavior

1. Build the Server Code into a COM .dll named MTSData.
2. Import the MTSData.dll and the MTSData.tlb as a component into a MTS Package. Be sure to mark the component as "Requires A New Transaction".
3. Place the Client Code in a program file.
4. Run the ClientCode.prg in two instances of Visual FoxPro.
5. Issue the following commands in the Command window of the first instance of Visual FoxPro:

         x.MoveNext
         x.ReturnRec(@aMTSRecord)
         DISPLAY MEMORY LIKE aMTSRecord
   								

6. Issue the following commands in the second instance of Visual FoxPro noting that the x.MoveNext command in the first instance moved the record pointer in this instance also.

         x.ReturnRec(@aMTSRecord)
         DISPLAY MEMORY LIKE aMTSRecord
   
   
   
         ********************Server Code********************************
         DEFINE CLASS MTSData AS FORM OLEPUBLIC
            PROCEDURE INIT
               SET DEFAULT TO "C:\MTSTest"
   
               OPEN DATABASE MTSData SHARED
               USE MTSTest SHARED
            ENDPROC
            PROCEDURE movenext
               SKIP 1
            ENDPROC
            PROCEDURE moveprev
               SKIP -1
            ENDPROC
            PROCEDURE movefirst
               GO TOP
            ENDPROC
            PROCEDURE movelast
               GO BOTTOM
            ENDPROC
            PROCEDURE returnrec
               LPARAMETER MyArray
               EXTERNAL ARRAY MyArray
               MyArray(1,1)=fld1
               MyArray(2,1)=fld2
               MyArray(3,1)=fld3
            ENDPROC
         ENDDEFINE
         ********************End Server Code****************************
   
         ********************Client Code********************************
         PUBLIC x
         PUBLIC aMTSRecord(3,1)
         x=CREATEOBJECT("MTSData.MTSData")
         COMARRAY(x,11) &&Sets the arrays passed to object X as 1 based
                        &&passed by reference.
         x.movenext
         x.returnrec(@aMTSRecord)
         DISPLAY MEMORY LIKE aMTSRecord
         ********************End Client Code****************************