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SQL Anywhere 11.0.0 » SQL Anywhere Server - SQL Usage » Monitoring and Improving Database Performance » Monitoring and improving performance » Performance improvement tips » Use the cache to improve performance


Dynamic cache sizing

SQL Anywhere provides automatic resizing of the database cache. The capabilities are different on different operating systems. On Windows and Unix operating systems, the cache grows and shrinks. Details are provided in the following sections.

Full dynamic cache sizing helps to ensure that the performance of your database server is not impacted by allocating inadequate memory. The cache grows when the database server can usefully use more, as long as memory is available, and shrinks when cache memory is required by other applications, so that the database server does not unduly impact other applications on the system. The effectiveness of dynamic cache sizing is limited, of course, by the physical memory available on your system.

Generally, dynamic cache sizing assesses cache requirements at the rate of approximately once per minute. However, after a new database is started or when a file grows significantly, statistics are sampled and the cache may be resized every five seconds for thirty seconds. After the initial thirty second period, the sampling rate drops back down to once per minute. Significant growth of a file is defined as a 1/8 growth since the database started or since the last growth that triggered an increase in the sampling rate. This change improves performance further, by adapting the cache size more quickly when databases are started dynamically and when a lot of data is inserted.

Dynamic cache sizing removes the need for explicit configuration of database cache in many situations, making SQL Anywhere even easier to use.

When an Address Windowing Extensions (AWE) cache is used, dynamic cache sizing is disabled. You cannot use an AWE cache on Windows Mobile.

For more information about AWE caches, see -cw server option.

Dynamic cache sizing on Windows
Dynamic cache sizing on Unix