Setting the Number of Lock Spins


	BEA Home \| Events \| Solutions \| Partners \| Products \| Services \| Download \| Developer Center \| WebSUPPORT
	http://www.oracle.com/technology/documentation/index.html \| Site Map \| Search \| PDF Files \| Contact \| Glossary

Tuxedo Documentation \| Setting Up a BEA Tuxedo Application \| Local Topics \| Previous Topic \| Next Topic \| Contents

For some BEA Tuxedo system operations (such as service name lookups and transactions), the bulletin board must be locked for exclusive access: that is, it must be accessible by only one process. If a process or thread finds that the bulletin board is locked by another process or thread, it retries, or spins on the lock for SPINCOUNT number of times before giving up and going to sleep on a waiting queue. Because sleeping is a costly operation, it is efficient to do some amount of spinning before sleeping.

Characteristics of the SPINCOUNT Parameter

Though the value of the SPINCOUNT parameter is application- and system-dependent, it may be helpful to keep the following basic guidelines in mind:

A process on a uniprocessor system should not spin. If the bulletin board is locked when a uniprocessor process tries to access it, then the process with the lock should be allowed to run as quickly as possible. This is possible only if the newcomer process gives up immediately.
A SPINCOUNT value of 1 is appropriate for uniprocessors.
On multiprocessors, a good starting value is 5,000, but some customers have benefited from a SPINCOUNT value as high as 100,000.
Set the SPINCOUNT value and observe your application throughput. Because you can tune the SPINCOUNT value using the TMIB, you can adjust it while the system is running.