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Don Burleson Blog 








Longest Oracle RAC 24x7 continuous availability?

Oracle Database Tips by Donald Burleson

Question:  This database expert claims that Oracle 24x7 is a myth.  What's the record for continuous availability on an Oracle database?

Answer: Well, I personally know of one Oracle database that has been up-and-available for six years, and I know of many databases with 99.9999% availability.  I know of one database system that's been running without interrupting the end-users for over ten years (Using OPS and then RAC) with less than an 3 hours of total downtime in a decade (to roll-in the RAC upgrade).  I even know of an OPS database in the World Trade Center that failed-over to a mirrored database in New Jersey, the end-users experiencing no interruption, even though the entire World Trade Center data center was ground into tiny pieces.

Rolling upgrades are the last frontier for continuous availability

The problem of requiring a bounce to roll-in software upgrades has always been an issue for some shops who cannot even be down for one minute per decade.  With the new Oracle RAC rolling upgrades, I expect to see Oracle RAC systems that will never, ever be unavailable.

There are mainframe financial databases (IMS, IDMS/R) that have been 100% available for over 15 years, so I don't agree with this assertion:

"But the fact is, it is impossible for us to have a truly 24X7 system when we take a look at availability from individual usage patterns, administrative tasks, and the end user perspective."

I also disagree that it takes downtime to perform DBA activities like rebuilding indexes and reorganizing tables. Oracle has zero-downtime index rebuilding with dbms_redefinition and online index rebuilding:

"We have all administered databases that required us to fix some piece of data, rebuild an index, or restart our TNS listeners. Is this down time? I tend to think YES."

If you like Oracle tuning, see the book "Oracle Tuning: The Definitive Reference", with 950 pages of tuning tips and scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.




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