The Different Dataguard Modes of Protection for Managers

I was recently asked to provide a description of the various modes of operation possible with a standby configuration. This was needed to explain the setup to a group of non-technical managers.

The original setup of this companies dataguard configuration was Maximum Performance but the company was concerned about the potential data loss associated with running in an asynchronous mode.

Below is what I produced for them, nothing particularly revelatory here, but perhaps it might be useful for you if you are having this debate with your management team.

Introduction

When using an Oracle standby database for Business Continuity purposes there are 3 possible modes of operation for determining how the data is sent from the primary (the database currently being used to support the business queries) database to the standby (failover database to be used upon invocation of business continuity) database.

There are 2 synchronous modes and 1 asynchronous mode.

The various modes of operation of a standby are a real trade-off between data protection and impact on the primary systems.

Modes of Operation

The following table shows the options giving the benefits and drawbacks.

Mode of Operation

SYNC/

ASYNC

Benefits

Drawbacks

Maximum Protection

SYNC

Never any data loss, no data ever accepted on primary
without being on standby.

Slower response times on primary. Network disruption
between primary and secondary causes downtime of primary database.

Maximum Availability

SYNC

Updates must be on standby before accepted on primary,
network disruption means the primary continues running with updates sent to
standby when it is available again.

Slower response times on primary. Data loss possible if
network fails and then site fails.

Maximum Performance

ASYNC

No performance slowdown for applications on primary.

Data loss will happen

This customer is currently running in Maximum Performance mode, and thus the standby solution has minimal impact on the response times of the various applications.

There are 2 factors that would impact the application response if they moved to a higher level of data protection, the network latency and the network bandwidth. During normal operation, the response time of applications that make data changes would be impacted by the round trip time (rtt) to their standby

During periods of high volume activity, the bandwidth can become congested and this could lead to significant delay in response time.

Conclusion

If a higher level of data protection was deemed a business requirement I would advise a significantly larger network bandwidth to the Business Continuity site.

During normal running we typically see a transport lag (of data between the sites) of around 10 seconds and this would be the typical amount of data we would lose in a disaster situation. During high peaks of activity this can increase.

In determining to increase the protection mode of the configuration there is a real trade off between how much you value your data (for this customer it is a reputational issue as much as a financial consideration) and the impact on your normal day-to-day performance.

About these ads
Leave a comment

2 Comments

  1. I think that decreasing the number of users per router and installing more of them to increase overall bandwidth of a company is the way to go in order to achieve a higher level of protection. If a network’s running ASYNC on their server, it’s literally as if there is no backup protection. What’s the use? I think it’s essential in this day and age to make sure there’s a backup on site and a cold backup off site in the event of some digital catastrophic system failure or what not. True, the chances of this happening with IT personnel on site 24/7 isn’t as high, but it still exists. Better safe than sorry: SYNC with maximum protection…

    Reply
  2. vijay

     /  April 10, 2012

    Nice explanation :)

    Reply

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 53 other followers

%d bloggers like this: