oracle data dictionary

database: v$database, v$instance, v$version
shared server: v$queue, v$dispatcher, v$shared_server
tablespaces: dba_tablespaces, dba_data_files, dba_free_space
control files: v$controlfile, v$parameter, v$controlfile_record_section
datafiles: v$datafile, v$datafile_header, v$filestat, dba_data_files
segment : dba_segments
extents: dba_extents
redo threads, groups and numbers: v$thread, v$log, v$logfile
archiving status: v$database, v$log, v$archived_log, v$archive_dest
database instance: v$instance, v$parameter, v$system_parameter
user passwords: v$pwfile_users
processes: v$process, v$bgprocess,v$session,v$lock
rman recovery: v$recover_file
work area memory: v$pgastat, v$sysstat,v$sesstat.