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The SNAPSHOT feature includes a histogram of transaction times. Modifications were done to support the generalized collection and reporting of the histogram data. These routines will support a histogram capability for other SNAPSHOT measurements. We also added histograms of waiting times for blocked lock requests: one for waiting times for blocked data record lock requests, and one for waiting times for blocked index lock requests (please note that the index locks are not controlled by the user). There is a small amount of overhead associated with mutex calls to collect clean statistics.
The configuration file can change the default histogram intervals (box width) for the transaction time histogram (default of 50,000 µsec or 0.05 seconds) and the lock waiting time histograms (default of 10,000 µsec or 0.01 seconds):
