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Data caches in ASE hold the data, index, and log pages currently in use, as well as recently used pages in memory. These caches are critical in providing high levels of system performance as they effectively avoid expensive disk I/O. Inadequately sized data caches can increase the incidence of physical disk accesses, thereby affecting the performance of the Sybase server. Periodic monitoring of the usage of the data cache is essential to determine whether the cache needs to be resized or not.

This test auto-discovers the data caches on the Sybase server, and tracks the usage of each cache. Frequently used objects and objects that occupy the memory are listed in detailed diagnosis. For this test to work, make sure that the enable monitoring parameter is enabled.

Measurement	Description	Measurement Unit	Interpretation
Data_cache_hit_ratio	Indicates the hit ratio of each data cache in the Sybase server.	Pct	If the value of this measure is low, it indicates that too many physical reads are occurring on the Sybase server. If the problem persists, it could result in a serious contention for disk resources, which in turn, can cause the performance of the Sybase server to significantly deteriorate. You might want to consider resizing the data cache to avoid this adversity. The detailed diagnosis for this measure provides a list of objects that occupy the memory in cache, so that we can easily identify the objects that are consuming too much memory, and accordingly initiate corrective actions.
Num_of_objects	Indicates the number of objects in each cache.	number	Use the detailed diagnosis of this measure to view the list of objects in cache; this reveals the objects that are frequently accessed by users.