eG Monitoring
 

Measures reported by DbIOCacheTest

The DBIOCacheTest monitors the I/O Buffer Cache on the MaxDB server. The database system uses the I/O buffer cache to manage all of the main memory that is available for I/O operations. The converter and the data cache are the most important main memory consumers that the database system manages in the I/O buffer cache. The converter is where the database system keeps information about which logical page number is saved at what physical position (MaxDB block address). When the database system fails to find a page number in the data cache, it searches for the page number in the converter and uses this to calculate the physical position of the data page in the data volumes. If the converter grows while the database is running, and requires more pages, the database system gives it more pages from the I/O buffer cache. If no more pages are available there, data is displaced from the data cache and made available to the converter.

Measurement Description Measurement Unit Interpretation
Total_IO_cache_size The current size of the I/O buffer cache MB  
Data_cache_size The portion of the I/O buffer cache that is currently utilized by the data cache MB A high value of this measure is imperative to ensure a high data cache hit rate. If the value of this measure is very low, it is recommended that you reset the CACHE_SIZE parameter.
Percent_data_cache The percentage of the I/O buffer cache used by the data cache Percent A high value of this measure is imperative to ensure a high data cache hit rate. If the value of this measure is very low, it is recommended that you reset the CACHE_SIZE parameter.
Converter_size The space in the I/O buffer cache currently used by the converter MB  
Percent_converter_size The percentage of the I/O buffer cache used by the converter Percent If the value of this measure falls, data is displaced from the data cache and made available to the converter.
IO_mgmt_size The current size of the I/O management MB  
File_directory_size The space currently used by the file directories MB  
Restart_record_size The space currently used by restart records that store all information that the database system requires to restart the database instance MB  
Block_allocator_size The amount of memory currently used by block allocators MB  
Unused_size The free space in the I/O buffer cache MB Ideally, this value should be high. A very low value of this measure indicates the need to reset the CACHE_SIZE.