V$DATABASE Queries

To get database identifier and database name:
SQL> select DBID, NAME from v$database;

DBID NAME
---------- ---------
3235629315 WORK

To retrieve current sequence change number:
SQL> select current_scn from v$database;

To check whether database is in archive log mode or not:
SQL> select log_mode from v$database;

LOG_MODE
------------
NOARCHIVELOG

To verify that forced logging (instructing Oracle Database to force all logging of changes to the redo, even if nologging or unrecoverable data loads are performed) has been enabled on your primary database:
SQL> select force_logging from v$database;