Memory issue with query of huge table from Oracle database with ADO in Excel VBA

Question

I need to use VBA to query a big data table (2.000.000 rows and 130 columns) from Oracle database and save it into text file.

The code I am using is the following

Dim DBConnection As ADODB.connection
Dim RecordSet As ADODB.RecordSet

'prepare string for connection
Dim strConnection As String
strConnection = "DRIVER=Oracle in OraClient11g_Home32;SERVER=" & database & " ;UID=" & username & ";PWD=" & password & ";DBQ=" & database & ";"

Set DBConnection = New ADODB.connection

'open connection
With DBConnection
    .CommandTimeout = False
    .ConnectionString = strConnection
    .CursorLocation = adUseClient
    .Open
End With


Set RecordSet = New ADODB.RecordSet
RecordSet.Open strSQLQuery, DBConnection, adOpenForwardOnly, adLockReadOnly

Do While RecordSet.EOF = False

    str = ""
    For x = 0 To RecordSet.Fields.Count - 1
        If IsNumeric(RecordSet.Fields(x).Value) Then
            dx = RecordSet.Fields(x).Value
            str = str & Format(dx, "0.############") & delimiter
        Else
            str = str & RecordSet.Fields(x).Value & delimiter
        End If
    Next x
    Print #FH, str

    RecordSet.MoveNext

Loop

The problem is that probably ADO tries to store in the recordset all the queried data, which will be several GB of data, thus using too much RAM.

I need to find a way to limit the number of rows that are stored in RAM at one time, so that I can download and save as many row as I want without having any issue with the RAM.

I researched but I cannot find anything about this.

Thank you.

Answer 1

May be you should try setting CursorLocation to adUseServer...