Controlling Connections Established by Database Links
Tracing can be done using – ALTER SYSTEM SET EVENTS ‘2049 trace name ERRORSTACK level 3’;
Nice note from MOS.
Commit after select from dblink – blocking lock.
Session 1:
++++++++++
04:44:51 ARROW:(DEMO@leo):PRIMARY>
04:45:30 ARROW:(DEMO@leo):PRIMARY> select name from v$pdbs@mdinh_april;
NAME
------------------------------
APRIL
Elapsed: 00:00:00.01
04:45:36 ARROW:(DEMO@leo):PRIMARY> commit;
Commit complete.
Elapsed: 00:00:00.00
04:45:41 ARROW:(DEMO@leo):PRIMARY>
04:45:49 ARROW:(DEMO@leo):PRIMARY> update t set id=-9999;
++++++++++
Session 2:
04:45:18 ARROW:(DEMO@leo):PRIMARY> update t set id=100;
1 row updated.
Elapsed: 00:00:00.00
04:45:21 ARROW:(DEMO@leo):PRIMARY> @/media/sf_working/sql/b.sql
STATE USERNAME SID_SERIAL SQL_ID SEQ# EVENT STATUS MIN MACHINE OSUSER PROGRAM
---------- --------------- ------------ ------------- ------ -------------------- -------- ---- -------------------- ---------- ---------------
BLOCKING DEMO 32,17 74nhxnyztg454 402 SQL*Net message to c ACTIVE 0 arrow.localdomain oracle sqlplus@arrow.l
WAITING *DEMO 41,271 1qfpvr7brd2pq 113 enq: TX - row lock c ACTIVE 8 arrow.localdomain oracle sqlplus@arrow.l
Elapsed: 00:00:00.01
STATE USERNAME SQL_ID SQL_TEXT
---------- --------------- ------------- --------------------------------------------------------------------------------
BLOCKING DEMO 7741d4und71ph with s as ( SELECT decode(level,1,'BLOCKING','WAITING') state, LPAD('*',(level-1
WAITING *DEMO 1qfpvr7brd2pq update t set id=-9999
Elapsed: 00:00:00.00
04:54:19 ARROW:(DEMO@leo):PRIMARY> select count(*) from t;
COUNT(*)
----------
1
Elapsed: 00:00:00.01
05:00:49 ARROW:(DEMO@leo):PRIMARY>
No commit after select from dblink – ORA-02049: timeout: distributed transaction waiting for lock.
Session is automatically killed based on database paraneter tributed_lock_timeout (default is 60s)
Session 1:
++++++++++
21:58:06 ARROW:(DEMO@leo):PRIMARY> update t set id=100;
1 row updated.
Elapsed: 00:00:00.01
21:58:14 ARROW:(DEMO@leo):PRIMARY>
Session 2:
+++++++++
21:58:45 ARROW:(DEMO@leo):PRIMARY> select name from v$pdbs@mdinh_april;
NAME
------------------------------
APRIL
Elapsed: 00:00:00.00
21:58:51 ARROW:(DEMO@leo):PRIMARY> update t set id=1;
update t set id=1
*
ERROR at line 1:
ORA-02049: timeout: distributed transaction waiting for lock
Elapsed: 00:01:00.01
21:59:59 ARROW:(DEMO@leo):PRIMARY>
Don’t forget to commit or rollback after using dblinks.
UPDATED: Tried to determine if there was a way to monitor distributed transaction and in this test case was not able to.
Session 1:
++++++++++
15:59:32 ARROW:(MDINH@leo):PRIMARY> update demo.t set id=100;
1 row updated.
Elapsed: 00:00:00.01
15:59:43 ARROW:(MDINH@leo):PRIMARY>
Session 2: Distributed Transaction
++++++++++
16:00:43 ARROW:(DEMO@leo):PRIMARY> select name from v$pdbs@mdinh_april;
NAME
------------------------------
APRIL
Elapsed: 00:00:00.00
16:00:47 ARROW:(DEMO@leo):PRIMARY> update t set id=-9999;
update t set id=-9999
*
ERROR at line 1:
ORA-02049: timeout: distributed transaction waiting for lock
Elapsed: 00:10:00.00
16:10:57 ARROW:(DEMO@leo):PRIMARY> update t set id=-9999;
update t set id=-9999
*
ERROR at line 1:
ORA-02049: timeout: distributed transaction waiting for lock
Elapsed: 00:10:00.01
16:23:03 ARROW:(DEMO@leo):PRIMARY>
Session 3: Monitoring
++++++++++
16:21:23 ARROW:(SYS@leo):PRIMARY> show parameter distributed_lock_timeout
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
distributed_lock_timeout integer 600
16:21:35 ARROW:(SYS@leo):PRIMARY> @b.sql
STATE USERNAME SID_SERIAL SQL_ID SEQ# EVENT STATUS MIN MACHINE OSUSER PROGRAM
---------- --------------- ------------ ------------- ------ -------------------- -------- ---- -------------------- ---------- ---------------
BLOCKING MDINH 26,3 32 SQL*Net message from INACTIVE 22 arrow.localdomain oracle sqlplus@arrow.l
WAITING *DEMO 16,23 1qfpvr7brd2pq 70 enq: TX - row lock c ACTIVE 9 arrow.localdomain oracle sqlplus@arrow.l
Elapsed: 00:00:00.01
STATE USERNAME SQL_ID SQL_TEXT
---------- --------------- ------------- --------------------------------------------------------------------------------
BLOCKING MDINH 4cnt32uym27j2 update demo.t set id=100
WAITING *DEMO 1qfpvr7brd2pq update t set id=-9999
Elapsed: 00:00:00.00
16:21:38 ARROW:(SYS@leo):PRIMARY> @b.sql
STATE USERNAME SID_SERIAL SQL_ID SEQ# EVENT STATUS MIN MACHINE OSUSER PROGRAM
---------- --------------- ------------ ------------- ------ -------------------- -------- ---- -------------------- ---------- ---------------
BLOCKING MDINH 26,3 32 SQL*Net message from INACTIVE 22 arrow.localdomain oracle sqlplus@arrow.l
WAITING *DEMO 16,23 1qfpvr7brd2pq 70 enq: TX - row lock c ACTIVE 9 arrow.localdomain oracle sqlplus@arrow.l
Elapsed: 00:00:00.01
STATE USERNAME SQL_ID SQL_TEXT
---------- --------------- ------------- --------------------------------------------------------------------------------
BLOCKING MDINH 4cnt32uym27j2 update demo.t set id=100
WAITING *DEMO 1qfpvr7brd2pq update t set id=-9999
Elapsed: 00:00:00.00
16:22:10 ARROW:(SYS@leo):PRIMARY> @b.sql
STATE USERNAME SID_SERIAL SQL_ID SEQ# EVENT STATUS MIN MACHINE OSUSER PROGRAM
---------- --------------- ------------ ------------- ------ -------------------- -------- ---- -------------------- ---------- ---------------
BLOCKING MDINH 26,3 32 SQL*Net message from INACTIVE 23 arrow.localdomain oracle sqlplus@arrow.l
WAITING *DEMO 16,23 1qfpvr7brd2pq 70 enq: TX - row lock c ACTIVE 10 arrow.localdomain oracle sqlplus@arrow.l
Elapsed: 00:00:00.01
STATE USERNAME SQL_ID SQL_TEXT
---------- --------------- ------------- --------------------------------------------------------------------------------
BLOCKING MDINH 4cnt32uym27j2 update demo.t set id=100
WAITING *DEMO 1qfpvr7brd2pq update t set id=-9999
Elapsed: 00:00:00.00
16:22:56 ARROW:(SYS@leo):PRIMARY> @b.sql
no rows selected
Elapsed: 00:00:00.01
no rows selected
Elapsed: 00:00:00.00
16:23:12 ARROW:(SYS@leo):PRIMARY>
