Performance Considerations

You can change the block size used in a Btree to affect the height or number of levels in a Btree collection.

Theory and test show that minimizing the height of a Btree reduces both the search and update time for Btree operations.

The improvements occur in the following areas.

• Reduced CPU time for Btree operations when Btree is cache-resident

• Improvements in overall disk and network retrieval times, by reducing the number of fetches, mitigating the effects of transfer latency

However, you should consider the following potential negative effects.

• Increase in transaction journal sizes, because the entire collection block images are audited

• Increased object cache utilization for certain collection access patterns