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RE: log buffer space wait

From: <Avnish.Rastogi_at_providence.org>
Date: Wed, 03 Sep 2003 09:34:32 -0800
Message-ID: <F001.005CEA62.20030903093432@fatcity.com>


I have one question regarding these wait times, may be dump. In the following wait events what is the unit of measurement for Time, I believe its in seconds as per the documentation. If yes then here stats are collected for only 51.23 Minutes (Appx 3073 seconds), how come Oracle is showing 566,516 seconds wait for log buffer space. I would appreciate if someone can explain.  

Thanks    

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                                                       

-----Original Message-----
Sent: Tuesday, September 02, 2003 6:39 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    

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Author: <Avnish.Rastogi_at_providence.org
  INET: Avnish.Rastogi_at_providence.org

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Received on Wed Sep 03 2003 - 12:34:32 CDT

Original text of this message

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