Oracle-dblink improper use

1. Symptom

RAC cluster statistics on the number of sessions to a very large difference, and each database server node initiates a session high as 400+.

-- 查询会话数信息
select /*+ rule */  inst_id,count(*) cnt from gv$session group by inst_id;

select /*+ rule */  inst_id,username,machine,count(*) cnt from gv$session
group by inst_id,username,machine
order by 4;

2. Reasons

1) Check the session where there is a common use dblink, then check information dblink found a preferred example of the above connection string using dblink connection, although added load_balance parameters, not the expected result.

SELECT /*+ ORDERED */
 S.KSUSEMNM "O_HOSTNAME",S.KSUSEPID "O_SPID",--操作dblink用户信息
 G.K2GTITID_ORA "O_TXID",
 S.INDX "S_SID",S.KSUSESER "S_SERIAL#",--dblink session信息
 DECODE(BITAND(KSUSEIDL, 11),
               1,
               'ACTIVE',
               0,
               DECODE(BITAND(KSUSEFLG, 4096), 0, 'INACTIVE', 'CACHED'),
               2,
               'SNIPED',
               3,
               'SNIPED',
               'KILLED') "S_STATUS",
                S.KSUUDNAM "DBLINK_USER"
  FROM SYS.X$K2GTE G, SYS.X$KTCXB T, SYS.X$KSUSE S
 WHERE G.K2GTDXCB = T.KTCXBXBA
   AND G.K2GTDSES = T.KTCXBSES
   AND S.ADDR = G.K2GTDSES;

- dblink information

3. treatment program

1) on the application side dblink close the connection session;

2) Use tnsnames.ora modify the configuration tns dblink connector disposed on the database server, and the node corresponding to the address to write over the vip other remote nodes in VIP.