Db I/O Cache Test

The Db I/O Cache test 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.

Target of the test : A MaxDB server

Agent deploying the test : An external agent

Outputs of the test : One set of results for the MaxDB server being monitored.

Configurable parameters for the test

Parameter	Description
Test Period	How often should the test be executed.
Host	The host name of the server for which the test is to be configured.
Port	The port number to which the server is listening.
DatabaseName	The test connects to a database on MaxDB and extracts performance statistics from the system tables in the database. Therefore, provide the name of a database in the DatabaseName text box.
Username	Since users with the SYSDBA privilege alone are allowed access to system tables, specify the name of such a user against Username.
Password	Provide the Password that corresponds to the specified Username.
Confirm Password	Confirm the password by retyping it here.

Measurements made by the test

Measurement	Description	Measurement Unit	Interpretation
Total I/O cache size	Indicates the current size of the I/O buffer cache.	MB
Data cache size	Indicates 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	Indicates 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	Indicates the space in the I/O buffer cache currently used by the converter.	MB
Percent converter size	Indicates 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	Indicates the current size of the I/O management.	MB
File directory size	Indicates the space currently used by the file directories.	MB
Restart record size	Indicates 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	Indicates the amount of memory currently used by block allocators.	MB
Unused size	Indicates 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.