Configuration parameters that affect table I/O

The AUTO_READAHEAD configuration parameter changes the automatic read-ahead mode or disables automatic read-ahead for a query. In addition, the DATASKIP configuration parameter enables or disables data skipping.

Automatic read-ahead processing helps improve query performance by issuing asynchronous page requests when Informix® detects that the query is encountering I/O. Asynchronous page requests can improve query performance by overlapping query processing with the processing necessary to retrieve data from disk and put it in the buffer pool. You can also use the AUTO_READAHEAD environment option of the SET ENVIRONMENT statement of SQL to enable or disable the value of the AUTO_READAHEAD configuration parameter for a session.


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