Sybase 12.4.2 manual Balancing I/O, Raw I/O on Unix operating systems, 441

CHAPTER 12 Managing System Resources

•To set the maximum number of threads a single user will use, issue the command SET OPTION MAX_IQ_THREADS_PER_CONNECTION. This can be used to control the amount of memory a particular operation consumes. For example, the DBA can set this option before issuing an

INSERT or LOAD command.

Balancing I/O

This section explains the importance of balancing I/O on your system. It explains how to use disk striping and how to locate files on separate disks to gain better performance.

Raw I/O (on UNIX operating systems)

Most UNIX files systems divide disks into fixed size partitions. Partitions are physical subsets of the disk that are accessed separately by the operating system. Disk partitions are typically accessed in two modes: cooked mode (through the UFS file system) or raw mode. Raw mode (sometimes called character mode) does unbuffered I/O, generally making a data transfer to or from the device with every read or write system call. The UFS (cooked) mode is a UNIX file system and a buffered I/O system which collects data in a buffer until it can transfer an entire buffer at a time.

When you create a database or a dbspace, you can place it on either a raw device or a file system file. Adaptive Server IQ determines automatically from the pathname you specify whether it is a raw partition or a file system file. Raw partitions can be up to 128GB.

For more information, see “Working with databases”.

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