Pythian Group

Please feel free to submit the backup and recovery and DR topics you want to discuss – just mention in the comments and I’ll make sure they are on the agenda!

What: Sydney Oracle Meetup #4 – Backups, Recovery and Disasters
When: May 15, 2009 5:30 PM
Where: Our usual location in CBD see even page for details.

Meetup Description:

SOM #4 is about Oracle backup and recovery. As usual, Pizza and drinks arrive at 5:30PM and we start the presentation at 6PM. We should be out by 8:30PM with optional post-event program. It’s Friday night in the end! Read the rest of this entry . . .

So you have created your standby database using the RMAN DUPLICATE command, you have set the ARCHIVE_LAG_TARGET to maintain a minimum lag target, and you have sorted out those nasty datafile missing errors using automatic file management. You’ve even added standby redo logs to improve the Mean Time To Recovery (MTTR).

Now management are demanding to know why the standby periodically lags during the day. They have you on the phone and they are asking what the current redo apply rate is.

Luckily, you read the Pythian blog regularly, or like most people google for a solution or script to help out so you don’t reinvent the wheel.

Management’s first question was, does the standby redo apply rate lag during the day and if so, when. The following SQL script joins v$archived_log to v$dataguard_status, which contains the most recent messages from Data Guard. We join to that table to get the timestamp for when a specific archive log started to be applied.

rem Reports standby apply rate with lag
rem
select TIMESTAMP,completion_time "ArchTime",
SEQUENCE#,round((blocks*block_size)/(1024*1024),1) "SizeM",
round((TIMESTAMP-lag(TIMESTAMP,1,TIMESTAMP) OVER (order by TIMESTAMP))*24*60*60,1) "Diff(sec)",
round((blocks*block_size)/1024/ decode(((TIMESTAMP-lag(TIMESTAMP,1,TIMESTAMP)
OVER (order by TIMESTAMP))*24*60*60),0,1,
(TIMESTAMP-lag(TIMESTAMP,1,TIMESTAMP) OVER (order by TIMESTAMP))*24*60*60),1) "KB/sec",
round((blocks*block_size)/(1024*1024)/ decode(((TIMESTAMP-lag(TIMESTAMP,1,TIMESTAMP)
OVER (order by TIMESTAMP))*24*60*60),0,1,
(TIMESTAMP-lag(TIMESTAMP,1,TIMESTAMP) OVER (order by TIMESTAMP))*24*60*60),3) "MB/sec",
round(((lead(TIMESTAMP,1,TIMESTAMP) over (order by TIMESTAMP))-completion_time)*24*60*60,1) "Lag(sec)"
from v$archived_log a, v$dataguard_status dgs
where a.name = replace(dgs.MESSAGE,'Media Recovery Log ','')
and dgs.FACILITY = 'Log Apply Services'
order by TIMESTAMP desc;

Read the rest of this entry . . .