Originally posted by: SystemAdmin

I've got AIX 5.2 and implemented concurent IO.
Process A writes in the file "test" word "XXXX"
Process B writes in the same file word "YYYY"
When I open this file, there is randomly written "XYXYXY", but I need "XXXXYYYY" to be written.
What is the solution of this problem?
#AIX-Forum

Originally posted by: SystemAdmin

Normally you will see this used for databases
" Under Concurrent I/O, multiple threads can simultaneously perform
reads and writes on a shared file. This option is
intended primarily for relational database
applications, most of which will operate under
Concurrent I/O without any modification.
Applications that do not enforce serialization for
accesses to shared files should not use
Concurrent I/O, as this could result in data
corruption due to competing accesses."

This is exactly what you are seeing. You are writing with two separate processes to the same file.
Databases like Oracle guarantee that the database blocks are being written in the correct order

There is a nice write up which explains CIO and DIO nicely

http://www-03.ibm.com/systems/resources/systems_p_os_aix_whitepapers_db_perf_aix.pdf

What problem are you trying to resolve by using CIO
#AIX-Forum

Originally posted by: cd3lgado

Hi

In AIX enviroments what you need is a licenced software from IBM called GPFS (General Parallel File Systems) that has the necessary logic to manage concurrent write and read operations on the same file from different nodes.

Hope this helps
#AIX-Forum

Originally posted by: SystemAdmin

thx 4 help
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