Calculation Network Bandwidth for Oracle Data Guard Disaster Recovery (DR)

In the realm of disaster recovery (DR) planning, calculating the network bandwidth required for Oracle Data Guard is paramount. Ensuring seamless replication and efficient data synchronization between primary and standby databases hinges on accurate bandwidth estimations

 

Understanding Redo Generation Rate

At the heart of bandwidth calculation lies the average redo generation rate per second in the database. To ascertain this crucial metric, one approach is to query the DBA_HIST_SYSMETRIC_SUMMARY table:

 

SELECT AVG(MAXVAL)

FROM DBA_HIST_SYSMETRIC_SUMMARY

WHERE METRIC_NAME=’Redo Generated Per Sec’;

 

This query yields the average of maximum summary redo generation values over a period, providing a reliable baseline for bandwidth computation.

 

Bandwidth Calculation Formula

 Required bandwidth = ((REDO rate (in bytes per second) / 0.75) * 8) / 1,000,000 (in Mbps)

 

Here, the redo rate in bytes per second is divided by 0.75 to account for a 25% loss at the LAN level, representing internal cabling inefficiencies. Multiplying by 8 converts bytes to bits, and finally, dividing by 1,000,000 converts bits per second to Mbps.

 

Why Avoid V$SYSMETRIC_HISTORY?

While some opt to retrieve redo generation data from V$SYSMETRIC_HISTORY, it's essential to note its limitations. This view only provides records from the past few hours, potentially missing peak redo generation periods. Relying solely on recent data may lead to inaccurate bandwidth assessments.