Configuring Spinlock Ratio Parameters

Spinlock ratio parameters specify the number of internal system resources such as rows in an internal table, or cache, that are protected by one spinlock.

A spinlock is a simple locking mechanism that prevents a process from accessing the system resource currently used by another process. All processes trying to access the resource must wait (or “spin”) until the lock is released.

Spinlock ratio configuration parameters are meaningful only in multiprocessing systems. An SAP ASE configured with only one engine has only one spinlock, regardless of the value specified for a spinlock ratio configuration parameter.

This table lists system resources protected by spinlocks and the configuration parameters you can use to change the default spinlock ratio.

The value specified for a spinlock ratio parameter defines the ratio of the particular resource to spinlocks, not the number of spinlocks. For example, if 100 is specified for the spinlock ratio, SAP ASE allocates one spinlock for each 100 resources. The number of spinlocks allocated by SAP ASE depends on the total number of resources as well as on the ratio specified. The lower the value specified for the spinlock ratio, the higher the number of spinlocks.

Spinlocks are assigned to system resources either in a round-robin manner, or sequentially:

• Round-Robin Assignment
  Metadata cache spinlocks (configured by the open index hash spinlock ratio, open index spinlock ratio, and open object spinlock ratio parameters) use the round-robin assignment method.
• Sequential Assignment
  Table-lock spinlocks, configured by the table lock spinlock ratio parameter, use the sequential assignment method.