||Oracle Tips by Burleson
Oracle10g Grid Computing
Chapter 12 - RAC Design Considerations
Creating Efficient RAC Data Objects
techniques to improve the efficiency of data objects include:
Use as few
indexes as possible to optimize data retrieval from the RAC data
objects. Index node contention is the largest source of intra-node
block pings (or as Oracle calls them, intra-instance block transfers.)
Index maintenance causes a great deal of intra-node pinging.
automated freelist management.
insert objects, pre-allocate extents to avoid dynamic space
management. Assign allocated extents to specific instances. This
avoids intra-instance block transfers during insert activity from
multiple nodes. For example:
EXTENT ( SIZE 200K
managed tablespaces to avoid uet$ and fet$ block pinging between
reverse-key indexes for indexes that may become right-hand indexes due
to high insert rates. (Note: This removes the capability to use index
scans. Use only when required.)
indexes such that the clustering factor is as close to the number of
used blocks as is possible. Testing various column orders in
concatenated indexes does this. In single column indexes required for
SQL optimization, consider re-ordering the table in index order to
reduce clustering factor. (Note: This technique can result in hot
blocks and is the reverse of the previous suggestion to use
reverse-key indexes, which actually increases the clustering factor.)
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