db_Writer performance

From: hopehope_123 <hopehope_123_at_yahoo.com>
Date: 7 Mar 2006 23:46:19 -0800
Message-ID: <1141803979.647945.219740@e56g2000cwe.googlegroups.com>

Hi Group ,

Here are the values of db writer related wait events. According to the manuals, high value means bottleneck . But how can i decide what the high value is?

These outputs reflects the 8 hours period.

                  select * from gv$sysstat where name ='DBWR buffers scanned' or name='DBWR lru scans' order by inst_id

first run:

		  INST_ID                               NAME
                                   CLASS
  VALUE
1                                     DBWR lru scans
                              23583
1                                     DBWR buffers scanned
                           10287267
2                                      DBWR lru scans
                              6668
2                                     DBWR buffers scanned
                           4897092

after 8 hours:

INST_ID                              NAME
                            VALUE
1                                     DBWR lru scans
                            25583
1                                     DBWR buffers scanned
                          11369509
2                                     DBWR lru scans
                          6756
2                                    DBWR buffers scanned
                         4985046

select * from gv$system_event where event in ('buffer busy waits','db file parallel write','free buffer waits','write complete waits')

          order by 1

1.run:

  INST_ID                                EVENT
                                  TOTAL_WAITS
 TOTAL_TIMEOUTS                         TIME_WAITED
       AVERAGE_WAIT                           TIME_WAITED_MICRO

1                                      free buffer waits
                                605
492                                    53233
      88                                     532330815

1                                      write complete waits
                                17
14                                     1467
      86                                     14670866

1                                      buffer busy waits
                                326276
197                                    372973
      1                                      3729726693

2                                      free buffer waits
                                4137
3291                                   342129
      83                                     3421290680

2                                      write complete waits
                                359
165                                    19485
      54                                     194854301

2                                      buffer busy waits
                                812305
1244                                   757945
      1                                      7579448834

after 8 hours:

INST_ID                                EVENT
                                TOTAL_WAITS
TOTAL_TIMEOUTS                         TIME_WAITED
      AVERAGE_WAIT                           TIME_WAITED_MICRO

1                                      free buffer waits
                                901
579                                    64007
      71                                     640069129

1                                      write complete waits
                                23
18                                     1949
      85                                     19486573

1                                      buffer busy waits
                                417070
244                                    446700
      1                                      4466999220

2                                      free buffer waits
                                4376
3417                                   355618
      81                                     3556182943

2                                      write complete waits
                                390
192                                    22195
      57                                     221953503

2                                      buffer busy waits
                                829240
1621                                   911937
      1                                      9119370934





		  select * from gv$sysstat where name ='redo log space requests'

1.run:

  INST_ID                              NAME
 VALUE
2                                     redo log space requests
2619
1                                     redo log space requests

1823

after 8 hours:

INST_ID                               NAME
                              VALUE
2                                     redo log space requests
                              2978
1                                     redo log space requests
                              2220

Kind Regards,
tolga Received on Wed Mar 08 2006 - 01:46:19 CST