Concurrent I/O (AIX only)

On AIX® operating systems, you can use concurrent I/O in addition to direct I/O for chunks that use cooked files. Concurrent I/O can improve performance, because it allows multiple reads and writes to a file to occur concurrently, without the usual serialization of noncompeting read and write operations.

Concurrent I/O can be especially beneficial when you have data in a single chunk file striped across multiple disks.

Concurrent I/O, which you enable by setting the DIRECT_IO configuration parameter to 2, includes the benefit of avoiding file system buffering and is subject to the same limitations and use of KAIO as occurs if you use direct I/O without concurrent I/O. Thus, when concurrent I/O is enabled, you get both unbuffered I/O and concurrent I/O.

If Informix® uses concurrent I/O for a chunk, and another program (such as an external backup program) tries to open the same chunk file without using concurrent I/O, the open operation will fail.

Informix does not use direct or concurrent I/O for cooked files used for temporary dbspace chunks.

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