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RE: log buffer space wait

From: Cary Millsap <cary.millsap_at_hotsos.com>
Date: Tue, 02 Sep 2003 09:34:26 -0800
Message-ID: <F001.005CE8A5.20030902093426@fatcity.com>


http://www.ixora.com.au/q+a/0008/24162020.htm

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com

Upcoming events:

- Hotsos Clinic 101 in Sydney
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-----Original Message-----
DENNIS WILLIAMS
Sent: Tuesday, September 02, 2003 12:04 PM To: Multiple recipients of list ORACLE-L

Vivek

    Good question. At this point I haven't seen any replies to your request.
The specific wait points to the log buffer itself as being too small, not
particularly the redo logs themselves. Your init.ora parameters show this
buffer as being only 10-meg. I would suggest you increase it. But your redo
logs are only 10-meg themselves, so you should consider increasing the size
of the logs while you are at it or you may hit that as the next limit. Since
the redo logs are continuously written, it is usually recommended that they
be on a device that is devoted to redo logs.

Dennis Williams
DBA, 80%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Tuesday, September 02, 2003 8:39 AM To: Multiple recipients of list ORACLE-L

At a Benchmark a particular Processing + DML intensive batch Job
(Accounts

Interest Calculation) is experiencing

"log buffer space" wait .  

Config :-

On Solaris 9

Cpu_count = 72

Oracle 9.2

Online Redo logfiles are on a RAID 0+1 Volume (NOT Raw or RAID 1) Log_buffer
= 10 M

$ sar Command Outpuit %wio only about 6 % for Volume containing the redo logfiles

Database in NOARCHIVELOG mode  

Qs. How can we reduce this wait event ? Would RAW / RAID 1 for redo logfiles
help ?

Qs. Could this be a Bug ?  




STATSPACK report for  

DB Name DB Id Instance Inst Num Release Cluster Host

BM2           3727568246 bm2                 1 9.2.0.3.0   NO
sleepy  

            Snap Id Snap Time Sessions Curs/Sess Comment

Begin Snap: 240 01-Sep-03 03:09:41 23 1.5

  End Snap: 241 01-Sep-03 04:00:55 24 1.7

   Elapsed: 51.23 (mins)  

Top 5 Timed Events

~~~~~~~~~~~~~~~~~~                                                     %
Total
Event                                               Waits    Time (s)
Ela
Time
log buffer space                                1,817,258     566,516
56.24
latch free                                      2,964,652     334,120
33.17
log file sync                                      55,230      43,488
4.32
buffer busy waits                                  62,839      26,129
2.59
CPU time                                                       22,018
2.19

Wait Events for DB: BM2 Instance: bm2 Snaps: 240 -241

-> s - second

-> cs - centisecond - 100th of a second

-> ms - millisecond - 1000th of a second

-> us - microsecond - 1000000th of a second

-> ordered by wait time desc, waits desc (idle events last)  

                                                                   Avg

                                                     Total Wait   wait
Waits
Event                               Waits   Timeouts   Time (s)   (ms)
/txn
log buffer space                1,817,258        139    566,516    312
54.4
latch free                      2,964,652    892,594    334,120    113
88.8
log file sync                      55,230     21,210     43,488    787
1.7
buffer busy waits                  62,839     10,250     26,129    416
1.9    

Latch Activity for DB: BM2 Instance: bm2 Snaps: 240 -241  

                                           Pct    Avg   Wait
Pct
                              Get          Get   Slps   Time
NoWait
NoWait
Latch                       Requests      Miss  /Miss    (s)
Requests
Miss
post/wait queue                  97,357    4.7    0.4    577
1,871,155
249.5
process allocation                  751    7.2    3.0     10
747
0.5

process group creation 1,502 0.0 0 0

redo allocation 24,482,283 13.5 0.4 ###### 0

redo copy                       675,177   99.6    1.1 ######
21,986,833
708.0  

init.ora Parameters for DB: BM2 Instance: bm2 Snaps: 240 -241  

                                                                  End
value
Parameter Name                Begin value                       (if
different)

_db_block_lru_latches 128

audit_trail                   FALSE

background_dump_dest          /oracle/ora92-64/rdbms/log/bdump

compatible                    9.2.0.3

control_files                 /lbmdb02/bm2/data02/control_01_bm

core_dump_dest                /oracle/ora92-64/rdbms/log/cdump

cursor_sharing                EXACT

cursor_space_for_time         TRUE

db_block_size                 8192

db_cache_size                 1258291200

db_file_multiblock_read_count 32

db_files                      1500

db_keep_cache_size            117440512

db_name                       bm2

db_writer_processes           16

dml_locks                     10000

enqueue_resources             680000

hash_join_enabled             FALSE

java_pool_size                16777216

large_pool_size               16777216

log_buffer                    10485760

log_checkpoint_interval       0

log_checkpoint_timeout        0

log_checkpoints_to_alert      TRUE

max_dump_file_size            10240

max_rollback_segments         4000

nls_date_format               DD-MM-YYYY

open_cursors                  1000

open_links                    4

optimizer_index_cost_adj      15

optimizer_mode                CHOOSE

os_authent_prefix

parallel_max_servers 0

parallel_min_servers 0

processes                     3500

session_cached_cursors        50

sessions                      3855

shared_pool_reserved_size     52428800

shared_pool_size              536870912

sort_area_retained_size       2048576

sort_area_size                12582912

timed_statistics              TRUE

transaction_auditing          FALSE

undo_management               AUTO

undo_tablespace               TBA_UNDO

user_dump_dest                /oracle/ora92-64/rdbms/log/udump

utl_file_dir                  *

          -------------------------------------------------------------

 

End of Report    

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: DENNIS WILLIAMS
  INET: DWILLIAMS_at_LIFETOUCH.COM

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Received on Tue Sep 02 2003 - 12:34:26 CDT

Original text of this message

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