Tuning Data Guard Log Transfer Oracle Database Tips by Donald BurlesonDecember 9, 2015

Oracle Data Guard - Performance Tuning of Data Guard Configuration

Tuning the Log Transfer Service

The previous section presented a list of views that can provide data to diagnose performance issues in a Data Guard environment. In this section, the details on collecting and interpreting statistics for the log transfer process will be presented. Additionally, determining an optimal network bandwidth using these statistics will be covered in this section. A few tips that can be used to tune the Oracle Net and I/O system for better response time during the transfer of archived logs to standby destinations will also be included.

Performance Tuning of Data Guard Configuration

Gathering Log Transfer Related Statistics

Most of the log transfer related statistics can be obtained from the v$archived_log dynamic performance view. The script, Find_Archive_Time.sql, from the code depot will show the size of archived redo log files and their archival timing on local and remote archive destinations. A sample output from this script is shown below:

Find_Archive_Time.sql

-- *************************************************
-- Copyright © 2004 by Rampant TechPress
--
-- Desc: Script to find out the size of archived redo log file
--       And the archival time on local and remote achiving
--       Destinations.

set linesize 100

column destination     format a25 trunc
column thread#         format 99
column sequence#       format 999999
column sizeoffile      format 9999999
column completion_time format a20

select
   d.destination||'('||d.target||')' destination,
   l.thread#,
   l.sequence#,
   l.block_size*(l.blocks+1) sizeoffile,
   to_char(l.completion_time,'yyyy-mon-dd hh24:mi:ss') completion_time
from
   v$archived_log l,
   v$archive_dest d
See code depot for full scripts
order by
   THREAD#,SEQUENCE#,STANDBY_DEST;

Output from Find_Archive_Time.sql script:

DESTINATION               THREAD# SEQUENCE# SIZEOFFILE COMPLETION_TIME
-----------               ------- --------- ---------- ----------------
/oracle/appsdb/arch(PRIMA    1    1854     552448 2004-JAN-24 14:29:58
stdby2(STANDBY)              1    1854     552448 2004-JAN-24 14:29:58
appsstdby(STANDBY)           1    1854     552448 2004-JAN-24 14:53:24
/oracle/appsdb/arch(PRIMA    1    1855       1536 2004-JAN-24 14:31:19
stdby2(STANDBY)              1    1855       1536 2004-JAN-24 14:31:19
appsstdby(STANDBY)           1    1855       1536 2004-JAN-24 14:53:24
/oracle/appsdb/arch(PRIMA    1    1856      13312 2004-JAN-24 14:51:59
stdby2(STANDBY)              1    1856      13312 2004-JAN-24 14:51:59
appsstdby(STANDBY)           1    1856      13312 2004-JAN-24 14:51:59

Network Tuning for the Log Transport Service

Very few parameters can influence the performance of Oracle Net, and SDU is one of the most significant one that can. If network throughput is not sufficient, consider upgrading the network topology; however, in some cases it may not be easier to upgrade the network topology. In these circumstances, the DBA must evaluate the potential performance gain that can be achieved by reducing the network traffic.

How can the network traffic be decreased? In a Data Guard environment, transfer all the archived redo records to the standby site. This cannot be compromised. One possible solution is to compress the archived redo log files before sending them over to the standby site.

To some extent, Secure Shell port forwarding and compression can be used to reduce the size of archived redo log files. Since archived redo log files are in binary format, it may not be possible to achieve a huge compression ratio using Secure Shell. Moreover, the extra overhead in compression may outweigh the benefits achieved by reduction in network traffic. This option must be evaluated in the configuration before reaching a conclusion.

The Secure Shell port forwarding technique enjoys varied degrees of success depending on the size of redo log files and the nature of data protection mode. More information about using Secure Shell port forwarding in a Data Guard environment is available on Oracle's MOSC site at MOSC.oracle.com. More information about Secure Shell can be obtained from www.ssh.com.

For more information, check my notes on Oracle Network Tuning.

Data Guard Log Transfer Statistics Tips

Data Guard optimal network bandwidth Tips