. Net is connected to the db2 database through oledb and the built-in connection method of ibm. An error occurred while connecting to the db2 database.

First connection through ibm
DataSet ds = new DataSet ();
OleDbConnection cn = new OleDbConnection (
"Provider = IBMDA400.1; Data Source = 192.168.21.10; User ID = b4dd;" +
"Password = b4dd; Default Collection = QIBMPP ");
Cn. Open ();
OleDbDataAdapter adp = new OleDbDataAdapter ("select * from qibmpp. CUSTOM", cn );
Adp. Fill (ds, "0 ");
If (ds. Tables. Count> 0)
{
DataGridView1.Refresh ();
This. dataGridView1.DataSource = ds. Tables [0]. DefaultView;
}
Why is the following error displayed?
"IBMDA400.1" failed. No error message is available. Result code: E_UNEXPECTED (0x8000FFFF ).

Another connection through oledb
DataSet ds = new DataSet ();
OleDbConnection Conn = new OleDbConnection ("Provider = IBMDA400.DataSource. 1; Data Source = ibm.com.cn; Persist Security Info = True; User ID = sss; PASSWORD = ssss ");
Conn. Open ();
OleDbDataAdapter adp = new OleDbDataAdapter ("select * from QIBMPP. CUSTOM", Conn );
// Adp. Fill (ds, "cust ");
Adp. Fill (ds, "CUSTOM ");
If (ds. Tables. Count> 0)
{
DataGridView1.Refresh ();
This. dataGridView1.DataSource = ds. Tables [0]. DefaultView;

}
The following error message is displayed?
Try to read or write the protected memory. This usually indicates that other memory is damaged.

Could you help me solve this problem? Thank you, online, etc.