Monday, August 4, 2008

Running Parallel Db queries on huge Databases.

When the size of the table is very high and the column you are looking for is not indexed then the best way to run the query would be by parallel execution.

This really speeds up the process . But the catch here is that the CPU utilization is high and in production systems this may end up in locks.

This technique can be safely used in backup db servers.


SELECT /*+ parallel(huge_table,4 ) */ * FROM huge_table;

where 4 is the degree of parallelism.The degree of parallelism depends on the capacity of the machines.

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