MIssing data in v$backup_async_io and v$backup_sync_io

OS: AIX 5300-06 
Oracle: 9.2.0.8

I hit a strange problem. I had a problem with a performance of RMAN backup and according to Oracle Metalink note

Known RMAN Performance Problems [ID 247611.1]

RMAN incremental backup performance degrades over time in NOCATALOG mode
 
Version affected : 8.1  9.0.1
Version fixed    : 8174 9014 9201
Affects          : Target database
Diagnosis        : Many entries in X$KSFQP
Workaround    : SQL> alter system set events 'immediate trace name ksfqp_limit level 1';

I executed on RMAN session

RMAN> sql "alter system set events ''immediate trace name ksfqp_limit level 1''";


 
sql statement: alter system set events ''immediate trace name ksfqp_limit level 1''

After that I wanted to check a backup performance using the views v$backup_async_io and 

v$backup_sync_io but the datas weren`t up to date.

SQL> select max(open_time),max(close_time) from v$backup_async_io;
 
MAX(OPEN_TIME)      MAX(CLOSE_TIME)
------------------- -------------------
2011-05-31 10:26:39 2011-05-31 10:26:39
 


 
SQL> select max(open_time),max(close_time) from v$backup_sync_io;
 
MAX(OPEN_TIME)      MAX(CLOSE_TIME)
------------------- -------------------
2011-05-31 10:26:39 2011-05-31 10:26:39

Where are the data after 2011-05-31 10:26:39 ?

Let`s check an alert.log

...
Tue May 31 10:26:38 2011
Starting control autobackup
Tue May 31 10:28:01 2011
Control autobackup written to SBT_TAPE device
        comment 'API Version 2.0,MMS Version 5.4.1.0',
        media '2'
        handle 'c-1601303025-20110531-26'
Tue May 31 10:31:19 2011
OS Pid: 2113700 executed alter system set events 'immediate trace name ksfqp_limit level 1'
Tue May 31 10:41:01 2011
Thread 1 advanced to log sequence 59271
  Current log# 3 seq# 59271 mem# 0: /r655/oradata/XXX/redo03.log
  Current log# 3 seq# 59271 mem# 1: /r656/oradata/XXX/redo03.log
Tue May 31 10:41:01 2011
ARCH: Evaluating archive   log 2 thread 1 sequence 59270
ARCH: Beginning to archive log 2 thread 1 sequence 59270
Creating archive destination LOG_ARCHIVE_DEST_1: '/a655/app/oracle/admin/XXX/arch/1_59270.arch'
Tue May 31 10:41:01 2011
ARC0: Evaluating archive   log 2 thread 1 sequence 59270
ARC0: Unable to archive log 2 thread 1 sequence 59270
      Log actively being archived by another process
Tue May 31 10:41:01 2011
ARCH: Completed archiving  log 2 thread 1 sequence 59270
Tue May 31 10:41:58 2011
Starting control autobackup
Tue May 31 10:43:41 2011 
...

Indeed at 10:31:19 I set an event and it was stamped in the alert log.

On the metalink I found the note: Data missing from V$backup_async_io [ID 277605.1]

Symptoms
After taking Rman backup you do not see any data populated in v$backup_aysnc_io.

Cause
You have set this event in init.ora or session level 
alter system set events 'immediate trace name ksfqp_limit level 1

Fix
This Event limits the maximum number of rows in v$backup_[a]sync_io table setting it to 1, 
maximum number of rows is 0; by setting it to 2, 
maximum number of rows is 2 by setting it to 3, 
maximum number of rows is 4 (ie 2 power of (3-1)) and so on.

I fix the problem by executing

SQL> alter system set events 'immediate trace name ksfqp_limit level 20';


System altered.