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."
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