V$session and gV$session

Question

Can anyone explain v$session and gv$session ;

Answer 1

Prefix G in GV$ means GLOBAL. The best way to find out the the difference between v$session and gv$session is to look in v$fixed_view_definition.
V$SESSION
select SADDR,
       SID,
       SERIAL#,
       AUDSID,
  from GV$SESSION
where inst_id = USERENV('Instance')GV$SESSION
select s.inst_id,
       s.addr,
       s.indx,
       s.ksuseser,
       s.ksuudses,
       s.ksusepro,
       s.ksuudlui,
       s.ksuudlna,
       s.ksuudoct,
       s.ksusesow,
       decode(s.ksusetrn, hextoraw('00'), null, s.ksusetrn),
       decode(s.ksqpswat, hextoraw('00'), null, s.ksqpswat),
       decode(bitand(s.ksuseidl, 11),
              1,
              'ACTIVE',
              0,
              decode(bitand(s.ksuseflg, 4096), 0, 'INACTIVE', 'CACHED'),
              2,
              'SNIPED',
              3,
              'SNIPED',
              'KILLED'),
       decode(s.ksspatyp, 1, 'DEDICATED', 2, 'SHARED', 3, 'PSEUDO', 'NONE'),
       s.ksuudsid,
       s.ksuudsna,
       s.ksuseunm,
       s.ksusepid,
       s.ksusemnm,
       s.ksusetid,
       s.ksusepnm,
       decode(bitand(s.ksuseflg, 19),
              17,
              'BACKGROUND',
              1,
              'USER',
              2,
              'RECURSIVE',
       s.ksusesql,
       s.ksusesqh,
       s.ksusesqi,
       decode(s.ksusesch, 65535, to_number(null), s.ksusesch),
       s.ksusepsq,
       s.ksusepha,
       s.ksusepsi,
       decode(s.ksusepch, 65535, to_number(null), s.ksusepch),
       decode(s.ksusepeo, 0, to_number(null), s.ksusepeo),
       decode(s.ksusepeo, 0, to_number(null), s.ksusepes),
       decode(s.ksusepco, 0, to_number(null), s.ksusepco),
       decode(s.ksusepco, 0, to_number(null), s.ksusepcs),
       s.ksuseapp,
       s.ksuseaph,
       s.ksuseact,
       s.ksuseach,
       s.ksusecli,
       s.ksusefix,
       s.ksuseobj,
       s.ksusefil,
       s.ksuseblk,
       s.ksuseslt,
       s.ksuseltm,
       s.ksusectm,
       decode(bitand(s.ksusepxopt, 12), 0, 'NO', 'YES'),
       decode(s.ksuseft,
              2,
              'SESSION',
              4,
              'SELECT',
              8,
              'TRANSACTIONAL',
              'NONE'),
       decode(s.ksusefm, 1, 'BASIC', 2, 'PRECONNECT', 4, 'PREPARSE', 'NONE'),
       decode(s.ksusefs, 1, 'YES', 'NO'),
       s.ksusegrp,
       decode(bitand(s.ksusepxopt, 4),
              4,
              'ENABLED',
              decode(bitand(s.ksusepxopt, 8), 8, 'FORCED', 'DISABLED')),
       decode(bitand(s.ksusepxopt, 2),
              2,
              'FORCED',
              decode(bitand(s.ksusepxopt, 1), 1, 'DISABLED', 'ENABLED')),
       decode(bitand(s.ksusepxopt, 32),
              32,
              'FORCED',
              decode(bitand(s.ksusepxopt, 16), 16, 'DISABLED', 'ENABLED')),
       s.ksusecqd,
       s.ksuseclid,
       decode(s.ksuseblocker,
              4294967295,
              'UNKNOWN',
              4294967294,
              'UNKNOWN',
              4294967293,
              'UNKNOWN',
              4294967292,
              'NO HOLDER',
              4294967291,
              'NOT IN WAIT',
              'VALID'),
       decode(s.ksuseblocker,
              4294967295,
              to_number(null),
              4294967294,
              to_number(null),
              4294967293,
              to_number(null),
              4294967292,
              to_number(null),
              4294967291,
              to_number(null),
              bitand(s.ksuseblocker, 2147418112) / 65536),
       decode(s.ksuseblocker,
              4294967295,
              to_number(null),
              4294967294,
              to_number(null),
              4294967293,
              to_number(null),
              4294967292,
              to_number(null),
              4294967291,
              to_number(null),
              bitand(s.ksuseblocker, 65535)),
       s.ksuseseq,
       s.ksuseopc,
       e.kslednam,
       e.ksledp1,
       s.ksusep1,
       s.ksusep1r,
       e.ksledp2,
       s.ksusep2,
       s.ksusep2r,
       e.ksledp3,
       s.ksusep3,
       s.ksusep3r,
       e.ksledclassid,
       e.ksledclass#,
       e.ksledclass,
       decode(s.ksusetim,
              0,
              0,
              -1,
              -1,
              -2,
              -2,
              decode(round(s.ksusetim / 10000),
                     0,
                     -1,
                     round(s.ksusetim / 10000))),
       s.ksusewtm,
       decode(s.ksusetim,
              0,
              'WAITING',
              -2,
              'WAITED UNKNOWN TIME',
              -1,
              'WAITED SHORT TIME',
              decode(round(s.ksusetim / 10000),
                     0,
                     'WAITED SHORT TIME',
                     'WAITED KNOWN TIME')),
       s.ksusesvc,
       decode(bitand(s.ksuseflg2, 32), 32, 'ENABLED', 'DISABLED'),
       decode(bitand(s.ksuseflg2, 64), 64, 'TRUE', 'FALSE'),
       decode(bitand(s.ksuseflg2, 128), 128, 'TRUE', 'FALSE')
  from x$ksuse s, x$ksled e
where bitand(s.ksspaflg, 1) != 0
   and bitand(s.ksuseflg, 1) != 0
   and s.ksuseopc = e.indxAlexander Anokhin
http://alexanderanokhin.wordpress.com/