V$INSTANCE view provides one row of statistics for each Oracle instance running against the database : V_INSTANCE « System Tables Data Dictionary « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. System Tables Data Dictionary
3. V_INSTANCE

SQL> select instance_name, host_name, version,
  2     startup_time, round(sysdate-startup_time) "Days Up",
  3     status from v$instance;

INSTANCE_NAME
----------------
HOST_NAME
----------------------------------------------------------------
VERSION           STARTUP_T    Days Up STATUS
----------------- --------- ---------- ------------
xe
UBC-1
10.2.0.1.0        26-OCT-09          0 OPEN


SQL>