> "ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT FROM SESSION;"

This command is the same for both Active and regular Data Guard.  Other things control whether the Standby is readable or not (can't tell you which, though, because my organisation hasn't licenced A.D.G.!).

Yes, changes are replicated to the standby even before the archived redo log file is shipped to the standby server.

This is controlled by one or more archive_log_dest_* variables being configured to "know about" the standby database service (and, course, when the database fails over, the new primary will know about the old one).  These are the additional [service]_DGB services [statically] registered with the Listeners.

Regards,
   Phill  W.

This happened even if there is no logfile switch and the archve log in not yet in transport.

Data is not transported at the time of log switch it is done using Redo Transport Services

My Question is .....Does this mean that, when real life disaster and database failure happens,  I do not have data loss even if logs are not transported?

Log does not mean archived logs, it means redo logs which is transported using above given method based on your configuration for protection mode

Oracle Data Guard Protection Modes

For example in maximum protection mode, please refer above link to find more about all modes

 

Maximum Protection

 

This protection mode ensures that no data loss occurs if the primary database fails. To provide this level of protection, the redo data needed to recover a transaction must be written to both the online redo log and to the standby redo log on at least one synchronized standby database before the transaction commits. To ensure that data loss cannot occur, the primary database shuts down, rather than continue processing transactions, if it cannot write its redo stream to at least one synchronized standby database.

All three protection modes require that specific redo transport options be used to send redo data to at least one standby database.