||Oracle Database Tips by Donald Burleson
Oracle10g Grid Computing
Chapter 5 -
Preparing Shared Storage
To solve all these problems, the direct I/O is
highly desired. The way in which direct I/O is enabled varies from
one system to another and also depends on the type of file system
type. In some cases it is sufficient to set the filesystemio_options
parameter; in some cases a file system mount option is required; and
direct I/O can also be configured on a file-by-file basis using
special operating system commands. The use of ASM eliminates need
for direct I/O configuration.
When a system process attempts to read or write
using the normal synchronous read() or write() system calls, then it
must wait until the physical I/O is completed. Once the result of
the read/write operation, if success or failure, is understood the
process finishes the task. During this time, the execution of the
process is blocked while it waits for the results of the system
call. This is synchronous or blocking I/O.
However, the desired method is Asynchronous
I/O, which indicates that it is a 'Non-blocking I/O'. If the process
instead uses the asynchronous aio_read() or aio_write() system
calls, then the system call will return immediately once the I/O
request has been passed down to the hardware or queued in the
operating system, typically before the physical I/O operation has
even begun. It can continue executing and then receive the results
of the I/O operation later, once they are available. Thus, it is
asynchronous or non-blocking I/O.
Asynchronous I/O enables write intensive
processes like Oracle's DBWn to make full use of the I/O bandwidth
of the hardware, by queuing I/O requests to distinct devices in
quick succession so that they can be processed largely in parallel.
Asynchronous I/O also allows processes performing compute intensive
operations like sorts to pre-fetch data from disk before it is
required, so that the I/O and computation can occur in parallel.
The above text is
an excerpt from:
Oracle 10g Grid & Real Application
Computing with RAC
by Mike Ault, Madhu Tumma
can offer world-class remote Oracle database support at super-affordable prices.
Oracle DBA service provides 100% of the remote Oracle database administration
needs for your company, and includes 24x7 access to our staff of 100% OCP
Certified Oracle DBAs.
We require a 12 month service commitment and include the following services:
- Initial configuration review and problem identification
- Installation of Oracle statistics collection mechanisms and quarterly
database growth summaries
- Hourly monitoring of your Oracle database for pending problems
- Periodic performance analysis & identification of tuning activities
- Twenty Four hour Oracle emergency support
- Reporting and resolving all serious Oracle alert log messages
- Free use of the BC
- Quick response emergency support for production database outages
- Four hours of free remote DBA support every month. You can use these free
hours for any DBA activity, including database analysis, system design,
production migrations or personal mentoring.
information, please visit www.dba-oracle.com or email