记录一次ORA-38760_DG无法启动MRP进程
现象是监控报警称主备库日志应用不同步，登到备库查看mrp进程不存在，随即启动mrp进程，前台正常返回无报错，但是mrp进程还是没有启动起来。
如下：

前台执行

SQL> alter database recover managed standby database disconnect from session parallel 2;

Database altered.

正常返回，但是mrp进程没有启动
alert报错

Thu Oct 16 09:58:40 2014
MRP0: Background Media Recovery terminated with error 38760
Errors in file /oradata/diag/rdbms/xxxxxs2/xxxxxs2/trace/xxxxxs2_pr00_15195.trc:
ORA-38760: This database instance failed to turn on flashback database
Slave exiting with ORA-38760 exception
Errors in file /oradata/diag/rdbms/xxxxxs2/xxxxxs2/trace/xxxxxs2_pr00_15195.trc:
ORA-38760: This database instance failed to turn on flashback database
Recovery Slave PR00 previously exited with exception 38760
MRP0: Background Media Recovery process shutdown (xxxxxs2)
Completed: alter database recover managed standby database disconnect from session parallel 2

删除闪回恢复点后正常

SQL> select flashback_on from v$database;

FLASHBACK_ON
------------------
RESTORE POINT ONLY

SQL> select * from v$restore_point;

       SCN DATABASE_INCARNATION# GUA STORAGE_SIZE
---------- --------------------- --- ------------
TIME
---------------------------------------------------------------------------
RESTORE_POINT_TIME                                                          PRE
--------------------------------------------------------------------------- ---
NAME
--------------------------------------------------------------------------------
 629694310                     2 YES   5972688896
28-AUG-14 10.20.34.000000000 AM
                                                                            YES
RESTORE_POINT_TEST


SQL> drop restore point RESTORE_POINT_TEST;

Restore point dropped.

SQL> select flashback_on from v$database;

FLASHBACK_ON
------------------
NO

SQL> select open_mode from v$database;

OPEN_MODE
--------------------
MOUNTED

SQL> alter database flashback on;

Database altered.

SQL> alter database open read only;

Database altered.

SQL> alter database recover managed standby database disconnect from session parallel 2;

Database altered.

SQL> select open_mode from v$database;

OPEN_MODE
--------------------
READ ONLY WITH APPLY

alert日志如下：

Thu Oct 16 10:01:40 2014
Drop guaranteed restore point RESTORE_POINT_TEST
Stopping background process RVWR
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_9zx7369p_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_9zx9o5t7_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_9zyfjqh1_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b011w9p0_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b03pqqmd_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b06mkzpj_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_9zsfph8w_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_9zvs878h_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b097yjf1_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b0cwbpxt_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b0jwdp2q_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b0oc5tv6_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b0ybykqg_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b15z8ofj_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b1xll14q_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b1xll2f8_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b1xlmq41_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b22d11j4_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b25wkz7q_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b2htvobf_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b2tvdwdf_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b3bjxlm5_.flb
Deleted Oracle managed file /oradata/xxxxxs2/xxxxxs2/flashback/o1_mf_b3lhsznd_.flb
Guaranteed restore point RESTORE_POINT_TEST dropped
Thu Oct 16 10:02:17 2014
alter database recover managed standby database disconnect from session
Attempt to start background Managed Standby Recovery process (xxxxxs2)
Thu Oct 16 10:02:17 2014
MRP0 started with pid=26, OS id=15549 
MRP0: Background Managed Standby Recovery process started (xxxxxs2)
 started logmerger process
Thu Oct 16 10:02:22 2014
Managed Standby Recovery not using Real Time Apply
Parallel Media Recovery started with 40 slaves
Waiting for all non-current ORLs to be archived...
All non-current ORLs have been archived.
Media Recovery Log /oradata/archivelog/1_2047_788703924.dbf
Media Recovery Log /oradata/archivelog/2_2328_788703924.dbf
Completed: alter database recover managed standby database disconnect from session
Media Recovery Log /oradata/archivelog/2_2329_788703924.dbf
Media Recovery Log /oradata/archivelog/1_2048_788703924.dbf
Media Recovery Log /oradata/archivelog/2_2330_788703924.dbf
Thu Oct 16 10:02:37 2014
Media Recovery Log /oradata/xxxxxs2/xxxxxs2/archivelog/2014_10_16/o1_mf_1_2049_b3y859yy_.arc
Media Recovery Log /oradata/archivelog/2_2331_788703924.dbf
Media Recovery Log /oradata/archivelog/2_2332_788703924.dbf
Media Recovery Log /oradata/archivelog/1_2050_788703924.dbf
Media Recovery Log /oradata/xxxxxs2/xxxxxs2/archivelog/2014_10_16/o1_mf_2_2333_b3y924g8_.arc
Media Recovery Log /oradata/xxxxxs2/xxxxxs2/archivelog/2014_10_16/o1_mf_1_2051_b3y921rj_.arc
Media Recovery Log /oradata/archivelog/1_2052_788703924.dbf
Thu Oct 16 10:02:47 2014
Media Recovery Log /oradata/archivelog/2_2334_788703924.dbf
Media Recovery Waiting for thread 1 sequence 2053 (in transit)