*** How to migrate existing users from firebird 2.X to firebird 3? ***

Firebird 3 is using new method to validate users on the server.
Direct upgrade of security database is therefore impossible.
Described procedure will let you keep the list of firebird 2.X users
and all related information (firstname, lastname, etc.) except
password - new passwords will be generated randomly. Pay attention
that SYSDBA user is not touched - i.e. it will remain as was after
execution of upgrade procedure. In the commands below replace
'masterkey' with actual SYSDBA password for appropriate (2.X/3.0)
firebird server.

In firebird 2.5 backup security database:
  gbak -user sysdba -pas masterkey -b {host/path}security2.fdb security.fbk

In firebird 3 restore copy of 2.5 security database:
  gbak -user sysdba -pas masterkey -c security.fbk {host/path}security2.5
And run users upgrade sql script:
  isql -user sysdba -pas masterkey -i security_database.sql {host/path}security2.5
"security2.5" is a sample database name - you may use any other if you wish.

Script will create users with new random passwords and type them to you.
It's your responsibility to notify users about new passwords.
