The Open Method is inherited from FileType which is defined in OPC 10000-5.

The Open Method shall not support modes other than Read (0x01) and the Write + EraseExisting (0x06). If other modes are requested the return code is Bad_NotSupported.

If a transaction is in progress (see 7.10.9) on another Session then the Server shall return Bad_TransactionPending if Open is called with the Write Mode bit set. If the Server supports transactions, then the Server creates a new transaction or continues an existing transaction if Open is called with the Write Mode bit set.

If the SecureChannel is not authenticated the Server shall return Bad_SecurityModeInsufficient.

Method Result Codes

Result Code	Description
Bad_NotSupported	The mode is not supported.
Bad_TransactionPending	The TrustList cannot be opened because it is part of a transaction is in progress.
Bad_SecurityModeInsufficient	The SecureChannel is not authenticated.