Sqlbulkcopy Excessive Memory Consumtion even with EnableStreaming and low BatchSize - sql-server

Question

I try to bulk load data from Oracle to SqlServer through Powershell Sqlserver Module Sqlbulkcopy
On small Data, everything works fine, but on big Datasets, even if bachsize and streaming are set, sqlbulkcopy is taking all the memory available... until an out of memory
Also the notify function seems to give no answer, so I guess even with streaming=True, the process first load everything to memory...
What did I missed ?
$current = Get-Date
#copy table from Oracle table to SQL Server table
add-type -path "D:\oracle\product\12.1.0\client_1\odp.net\managed\common\Oracle.ManagedDataAccess.dll";
#define oracle connectin string
$conn_str = "cstr"
# query for oracle table
$qry = "
SELECT
ID,CREATEDT,MODIFIEDDT
FROM MYTABLE
WHERE source.ISSYNTHETIC=0 AND source.VALIDFROM >= TO_Date('2019-01-01','yyyy-mm-dd')
";
# key (on the left side) is the source column while value (on the right side) is the target column
[hashtable] $mapping = #{'ID'='ID';'CREATEDT'='CREATEDT';'MODIFIEDDT'};
$adapter = new-object Oracle.ManagedDataAccess.Client.OracleDataAdapter($qry, $conn_str);
#$info = new-object Oracle.ManagedDataAccess.Client;
#Write-Host ( $info | Format-Table | Out-String)
$dtbl = new-object System.Data.DataTable('MYTABLE');
#this Fill method will populate the $dtbl with the query $qry result
$adapter.Fill($dtbl);
#define sql server target instance
$sqlconn = "cstr";
$sqlbc = new-object system.data.sqlclient.Sqlbulkcopy($sqlconn)
$sqlbc.BatchSize = 1000;
$sqlbc.EnableStreaming = $true;
$sqlbc.NotifyAfter = 1000;
$sqlbc.DestinationTableName="DWHODS.MYTABLE";
#need to tell $sqlbc the column mapping info
foreach ($k in $mapping.keys)
{
$colMapping = new-object System.Data.SqlClient.SqlBulkCopyColumnMapping($k, $mapping[$k]);
$sqlbc.ColumnMappings.Add($colMapping) | out-null
}
$sqlbc.WriteToServer($dtbl);
$sqlbc.close;
$end= Get-Date
$diff= New-TimeSpan -Start $current -End $end
Write-Output "import needed : $diff"

Answer 1

Thanks to Jeroen, I changed the code like this, now its no more consuming memory :
$oraConn = New-Object Oracle.ManagedDataAccess.Client.OracleConnection($conn_str);
$oraConn.Open();
$command = $oraConn.CreateCommand();
$command.CommandText=$qry;
$reader = $command.ExecuteReader()
...
$sqlbc.WriteToServer($reader);