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Oracle RAC load balancing tips
Oracle Database Tips by Donald Burleson |
Question:
Is it possible in a RAC environment to force the database node
that you want to connect too?
Answer: Yes, and intelligent load balancing is an
important tuning technique. You use the tnsnames.ora file
to direct "like-minded" end-users to specific nodes, and you can
use TAF to specify failover nodes.
Again, in my years as a RAC DBA, I
recommend functional load balancing, whereby like-minded
transactions are grouped together on each node (e.g. one node
for order queries, one node for customer queries). Using
such a "functional" load balancing scheme, cache fusion pinging
is greatly reduced and performance is improved.
One major RAC tuning issue is minimizing pinging access the
cache fusion layer, and smart DBA's will segregate users by node
(i.e. customer queries on node 1, product queries on node 2,
etc).
I don't recommend that "automatic
load balancing" for all RAC databases, and it's smart to group
your end-users to nodes based on their query types.
Load-balancing for RAC involves
extensive manual configuration to use a round-robin
configuration to distribute the load among the instances.
Starting in Oracle 10g release 2, we have a brand-new
load-balancing advisory that promises to cut-down the manual
effort for RAC load balancing between instances, but this does
not take a functional approach to RAC load balancing, load
balancing by the "type" of data being requested.
Again, a "functional" load balancing scheme is best, especially
since pinging can become a major RAC bottleneck.
Here are
some notes on RAC load balancing:
