Does anybody know the event of "enq: DM - contention"?
my database is RAC, I'm doing the incompleted recovery, after I issued the command "alter database open resetlogs", it hung, and I got below mesage from v$session;
SID SERIAL# USERNAME EVENT MODULE BLOCKING_SESSION SQL_HASH_VALUE
----- ------- --------------- ------------------------------ ------------------------------ ---------------- --------------
726 17 SYS enq: DM - contention sqlplus@machine (TNS V1-V3) 726 2561034025
2191 11 SYS DIAG idle wait sqlplus@machine (TNS V1-V3) 2100190760
2204 1 gcs remote message 0
2203 1 gcs remote message 0
728 1 smon timer 0
1470 1 DIAG idle wait 0
2205 1 pmon timer 0
733 1 ges remote message 0
the strange thing here is that session 726 is blocking himself? and this session is running the command "alter database open resetlogs", here what the event "enq: DM - contention" mean here?