eG Monitoring
 

Measures reported by HanaCacheTest

cache that is right-sized and well-used can significantly boost database server performance! A cache is said to be effectively utilized only if it is able to service the maximum number of requests to the database; this greatly reduces direct disk accesses and related overheads, and thus improves database performance. On the contrary, ineffective cache usage can be the key contributor to a slowdown or degradation in server performance, as it increases disk accesses. To understand how the database caches are utilized and to promptly capture abnormalities in cache usage, administrators have to continuously monitor the size and usage of each of the database caches. The HanaCacheTest test helps administrators in this regard.

This test monitors each cache of the SAP HANA database server and reports its usage - both in terms of size and its request serving ability. In the process, the test proactively alerts administrators to the under-utilization and improper size of the cache, and helps them quickly initiate corrective measures.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
totalSizeMB Indicates the total size of this cache. MB  
usedSizeMB Indicates the space in the cache that is currently in use. MB Ideally, the value of this measure should be low. A high value or a consistent rise in the value is a sign that the cache is about to run out of space. If a cache does not have adequate space, it cannot hold additional entries, and hence cannot service requests properly. You may hence have to allocate more space to the cache or free-up space in the cache to accommodate more entries.
entryCount Indicates the number of entries i.e., requests or transactions that are available for retrieval from this cache. Number Ideally, the value of this measure should be high.
insertCount Indicates the number of INSERT entries that can be retrieved from this cache based on a received request. Number  
invalidateCount Indicates the number of INVALIDATE entries that can be retrieved from this cache based on a received request. Number  
hitCount Indicates the number of times this cache was hit for an entry without having to read from the disk during the last measurement period. Number A high value is desired for this measure. A low value or a consistent drop in this value is a cause for concern, as it indicates ineffective cache usage. This means high disk accesses, and poor server performance. One of the common reasons for bad cache usage is improper cache size. A cache that does not have sufficient space to accommodate entries will not be able to service requests effectively. You may hence have to allocate more space to the cache or free-up space in the cache to accommodate more entries.
missCount Indicates the number of times this cache was missed for an entry during the last measurement period. Number A low value is desired for this measure. A high value or a consistent increase in this value is a cause for concern, as it indicates ineffective cache usage. This means high disk accesses and poor server performance. One of the common reasons for bad cache usage is improper cache size. A cache that does not have sufficient space to accommodate entries will not be able to service requests effectively. You may hence have to allocate more space to the cache or free-up space in the cache to accommodate more entries.