RE: High "log buffer space" wait in BATCH Type Transactions

From: Asif Momen <asif_oracle_at_yahoo.com>
Date: Sun, 24 Feb 2008 03:12:15 -0800 (PST)
Message-ID: <82695.15488.qm@web56615.mail.re3.yahoo.com>

Hi Vivek,

"log buffer space" wait event occurs normally when Log Writer is too slow or when the log buffer is too small.

I think in your case LGWR is slow.

> Currently The Redo logfiles are on Mounted filesystem.

What is the OS block size of this mount point?

Did you enable CIO/DIO on this mount point?

How many redo log members do you have?

Regards

Asif Momen
http://momendba.blogspot.com

VIVEK_SHARMA <VIVEK_SHARMA_at_infosys.com> wrote: Folks

During a Benchmark Run on Batch Type Transactions on NON-RAC Database using Dedicated sessions following High "log buffer space" wait is seen. NOTE - Increasing log_buffer size from 7Mb to 32 Mb only resulted in a further REDUCED Performance.

Currently The Redo logfiles are on Mounted filesystem. Qs Will moving the Redo back to RAW Devices also Reduce the "log buffer space" wait wait for BATCH Runs?

NOTE - Previously, For OLTP type Transactions on the SAME Database, High "log file sync" wait was also seen with Redo on Mounted filesystem which disappreared when the Redo were moved to RAW Devices.

Oracle 10.2.0.3
Solaris 10

Will Share Statspack as needed please.

Cheers & Thanks

Vivek

Top 5 Timed Events                                                    Avg %Total
~~~~~~~~~~~~~~~~~~                                                   wait   Call
Event                                            Waits    Time (s)   (ms)   Time
----------------------------------------- ------------ ----------- ------ ------
log buffer space                             2,464,248     585,064    237   76.0
CPU time                                                   103,594          13.5
log file sync                                   48,470      30,062    620    3.9
buffer busy waits                              116,409      14,745    127    1.9
db file parallel write                       2,102,173      14,517      7    1.9
          -------------------------------------------------------------

^LHost CPU (CPUs: 120)

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Received on Sun Feb 24 2008 - 05:12:15 CST