NCLOB 4000 chars

Question

I am using Oracle Oledb provider to connet to a 9i database using ADO. One of the tables has a field of type NCLOB. When I try to write to the field data >4000 chars I get an error
ORA-24806 . The description of the error says
ORA-24806 LOB form mismatch
Cause: When reading from or writing into LOBs, the character set form of the user buffer should be same as that of the LOB.
Action: Make sure that the buffer you are using to read or write has the same form as that of the LOB.
But since I don't get this error for strings < 4000 chars, I assume all my settings ( char set etc) are Ok. This also should be the case since I am running the client on the same machine as server and the same home.
It also works if I change the field type to CLOB instead of NCLOB.
Has anybody used NCLOBS > 4000 chars with ADO ?

Answer 1

The original program is in C++. But here is a small VB test program I wrote to demonstrate the problem.
It works when I try to insert small strings but not large ones
The evnironment is
windows 2000 SP2
Oralce 9i (9.0.1.1)
Oracle oledb provider 9i
Ado version 2.5
Option Explicit
Dim Cn As ADODB.Connection
Dim CPw1 As ADODB.Command
Dim CPw2 As ADODB.Command
Dim Rs As ADODB.Recordset
Dim Conn As String
Dim QSQL As String
Private Sub cmdSend_Click()
Dim strl As String
Dim i As Integer
Set Rs = New ADODB.Recordset
Rs.CursorType = adOpenKeyset
Rs.LockType = adLockOptimistic
strl = "t"
For i = 1 To 4002
strl = strl + "t"
Next
Rs.Open "test1", Cn, , , adCmdTable
Rs.AddNew
Rs!ncol = strl
Rs.Update
Rs.Close
End Sub
Private Sub cmdcheck_Click()
Set Rs = New ADODB.Recordset
Rs.CursorType = adOpenForwardOnly
Rs.LockType = adLockReadOnly
' Set CPw2 = New ADODB.Command
With CPw2
.ActiveConnection = Cn
.CommandText = "Select * from test1"
.CommandType = adCmdText
.Execute
End With
Set Rs = CPw2.Execute
Rs.MoveFirst
MsgBox "Return value is " + Rs!ncol + " length is " + Len(Rs!ncol)
Rs.Close
End Sub
Private Sub Form_Load()
'You will need to replace the "*" with the appropriate values.
Conn = "Provider=OraOledb.Oracle;User ID=*;Data Source=*;password=*;Ndatatye=True"
Set Cn = New ADODB.Connection
With Cn
.ConnectionString = Conn
.CursorLocation = adUseClient
.Open
End With
QSQL = "Create table test1 (ncol nclob)"
Set CPw1 = New ADODB.Command
Set CPw2 = New ADODB.Command
With CPw1
.ActiveConnection = Cn
.CommandText = QSQL
.CommandType = adCmdText
' .Execute
' On Error Resume Next
End With
End Sub
Private Sub Form_Unload(Cancel As Integer)
Cn.Close
Set Cn = Nothing
Set CPw1 = Nothing
Set CPw2 = Nothing
End Sub
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