It's TRUE ... blocksize matters!
 

The use of multiple blocksizes in very large databases (VLDB) is more than 20 years old, and corporations have been using multiple blocksizes in the IDMS database with proven success since the 1980's.

For most databases, creating multiple blocksizes is not going to make a measurable difference, and the deployment of multiple blocksizes must be carefully evaluated on a case-by-case basis.  The DBA must carefully evaluate their database for I/O patterns and buffer efficiency to see if multiple blocksizes are right for their unique system.

While it is generally accepted that multiple blocksizes are not for every shop, they may be appropriate for large multi-terabyte databases where the DBA wants to incur the additional monitoring complexity to be able to control their I/O buffers at a lower-level of granularity.

What are the benefits of using multiple blocksizes?

Over the years, there have been heated discussions about the benefits of using multiple blocksizes, especially in these areas:

- Faster performance? - Some claim up to 3x faster elapsed times with a larger index blocksize.  See these TPC benchmarks that employed multiple blocksizes.  Vendors spend huge sums of money optimizing their systems for TPC benchmarks, so this indicates that they employed multiple blocksizes for a performance reason. 

- Faster updates - In 64-bit database with large data buffers (over 50 gig), some shops claim a benefit from segregating high-impact DML tables into a separate blocksize, assigned to a separate, small buffer.  They claim that this improved DML throughput because there are fewer RAM buffer chains to inspect for dirty blocks.

- Data segregation - Some DBA's use separate 2k data buffers for tablespaces that randomly fetch small rows, thereby maximizing RAM by not reading-in more data than required by the query.

Read more about the benefits of using multiple blocksizes here:

http://www.dba-oracle.com/t_multiple_blocksizes_summary.htm

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