UNIX for Dummies Questions & Answers

My HP-UX 11.0 system is supporting an Oracle database. I have found a number of references on the Net to the "Max I/O size" in relation to setting Oracle parameters.

How can I tell what my max i/o size is? I originally made the assumption that it was referring to my stripe size but now I think I may be mistaken.

You really need to ask Oracle this question. It could mean several things.

The maximum number of bytes that can be transferred in a single read or write system call is SSIZE_MAX which is 2 gigabytes in 11.0. A literal interpretation of your question would mean that you are looking for this value.

I am not a database expert, but I'm guessing that Oracle actually wants the maximum size of a physical disk operation. This value would come into play if you are giving Oracle raw disk sections that it will access directly via character special files. A disk driver written by HP will always transfer MAXPHYS bytes or less to or from the disk in exactly one disk operation. If you are using a disk drive that HP officially supports, that disk operation is guaranteed to complete even if the disk drive loses power during the operation. On 11.0, MAXPHYS is 256 kilobytes.

There are several other maxima that could loosely meet your definition, but you probably want one of the values mentioned above. And you should look up SSIZE_MAX (/usr/include/limits.h) or MAXPHYS (/usr/include/machine/param.h) on your system to be sure that you are getting the correct values.