Search notes:

Oracle: DBA_TAB_IDENTITY_COLS

user_tab_identity_cols, all_tab_identity_cols and dba_tab_identity_cols describe identity columns. 
select
   idc.table_name,
   idc.column_name,
   idc.generation_type,
   tac.default_on_null,
   idc.sequence_name,
   seq.last_number,
   tac.data_default,
   idc.identity_options
from
   user_tab_identity_cols idc                                                      join
   user_tab_columns       tac on idc.table_name    = tac.table_name     and
                                 idc.column_name   = tac.column_name               join
   user_sequences         seq on idc.sequence_name = seq.sequence_name

See also

data dictionary

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