Db Data Cache Test

The Db Data Cache test monitors the usage of the data cache on MaxDB. The data cache contains the last read- or write-accessed pages of the data volumes. It is shared by all simultaneously active users.

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
Data cache hit ratio	Indicates the percentage of successful accesses to the data cache.	Percent	A high hit rate of at least 98% is recommended for the data cache. If the hit rate is low, consider changing the size of the data cache.
Cache usable size	Indicates the current size of the data cache.	MB	The size of the data cache has the following effect on the performance of the database system: A large data cache makes a high hit rate possible. If the data cache is too large for a small main memory, this can lead to operating system swapping with a very high level of I/O activity. However, since the data cache is dynamically dimensioned by the database system, you cannot configure the size of the data cache directly, but can only influence it implicitly by configuring the I/O buffer cache. The database system takes the pages required for the data cache from the I/O buffer cache. If the other I/O buffer cache user, the converter, grows in size, the database system decreases the size of the data cache, if necessary.
Cache used size	Indicates the currently utilized portion of the data cache.	MB	If converter cache or catalog cache run out of space, the data cache is used; so, it is recommended that you increase the overall cache size.
Percent of data cache used	Indicates the percentage of the cache that is utilized.	Percent	If converter cache or catalog cache run out of space, the data cache is used; so, it is recommended that you increase the overall cache size.
Oms data size	Indicates the size of the data cache that is currently used for storing OMS data.	MB	Since the data in an SAP liveCache database instance consists mainly of OMS data, you should configure the data cache for SAP liveCache database instances to be large enough to store all the OMS data, if possible.
History data size	Indicates the size of the data cache required for consistent reads and transactions management.	MB
SQL data size	Indicates the size of the data cache not required either for OMS data or consistent reads and transaction management.	MB