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5-16 IBM Informix OnLine Database Server Administrator’s Guide
How Is Tuning Done?
How Is Tuning Done?
If the value of Pages/IO is 75 percent or more of Bufsize, each write to the
disk is, on average, deferred until the buffer is almost full. (Since the value of
Pages/IO is an average, some writes might be closer to 100 percent of the
buffer. The logging status affects this value; see the preceding paragraph.)
In this case, you can try to further improve buffer efficiency by increasing the
size of the buffer to accommodate more data before each write.
If the value of Pages/IO is less than 75 percent of Bufsize, writes to the disk
occur, on average, long before the buffer is fully used. In this case, you can try
to improve buffer efficiency by decreasing the size of the buffer to more
closely approximate the size of Pages/IO. Decreasing the size of the buffer
frees shared-memory space for other uses.
Refer to page 3-93 for further information about how to change the size of the
logical log or physical log buffer.