How to handle Legacy Systems if no Audit Trail is available or a "User Login" is not possible?

Problem statement: How to handle Legacy Systems if no audit trail is available or a "user login" is not possible?

First of all, it can be deduced from the contents of the EU GMP Guidelines Annex 11 that an audit trail in connection with GMP-relevant data and their modification should be available in a computerised system. If this functionality was not yet available at the time the system was purchased, it should first be checked whether an update with the audit trail functionality is now available for this system. If this is not the case, an appropriate alternative should be introduced. EU GMP Annex 11 does not describe what this alternative should look like.

Possible solution:

One possibility would be to use handwritten audit trail logbooks. This alternative is also proposed by the PIC/S document PI 041 GOOD PRACTICES FOR DATA MANAGEMENT AND INTEGRITY IN REGULATED GMP/GDP ENVIRONMENTS:
 
9.4 Audit trails for computerised systems:
If no electronic audit trail system exists a paper based record to demonstrate changes to data may be acceptable until a fully audit trailed (integrated system or independent audit software using a validated interface) system becomes available. These hybrid systems are permitted, where they achieve equivalence to integrated audit trail, such as described in Annex 11 of the PIC/S GMP Guide.

Source: PIC/S PI 041