System::getDbDiskCacheStats Method

getDbDiskCacheStats(jdo: JadeDynamicObject input);

The System class getDbDiskCacheStats method returns statistics relating to the persistent database cache. The values are returned as Integer64 properties in the dynamic object specified by the jdo parameter.

The returned values are Integer64 values representing counts of actions pertaining to the persistent database cache, most of which are cumulative, starting from when the database was opened. JADE applications that use the getDbDiskCacheStats method defined in the System class therefore need to compare values from one call to the next, to work out the value differences.

The properties returned in the dynamic object are listed in the following table.

Property	Description
cacheMisses	The number of cache misses; that is, where the address referenced a block that was not found in the cache
gets	The number of read requests received
puts	The number of write requests received
blockReads	The number of block reads from disk performed
getsWithFetch	The number of read requests with additional block prefetch received
putsWithFetch	The number of write requests with additional block prefetch received
blocksFetched	The number of blocks prefetched with read from disk
blockReadsMultiple	The number of prefetch reads performed
bufferReassigns	The number of times buffers were reassigned for use with a different address
bufferSteals	The number of times the buffer reassigned was dirty, requiring writing
maxHashCollisions	The maximum number of hash collisions
maxConcFlushIos	The maximum number of concurrent flush write operations
blockWrites	The number of single block writes to disk performed
blockWritesMultiple	The number of multiple block writes to disk performed

For further explanation of these values, refer to the JADE Monitor knowledge base.

Properties are added to the object when the method is first called. The object can then be used in subsequent calls. If the dynamic object passed to the method already contains properties that do not match the properties to be returned, the existing dynamic object properties are removed and replaced with the appropriate properties. This method is most efficient when the properties match those to be returned.

For an example of the use of and output from this method, see the System class getDbDiskCacheStats method in Volume 2 of the JADE Encyclopaedia of Classes.