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SNAPSHOT_LOGFLUSHTIME_USEC <histogram interval width in microseconds>
The SNAPSHOT feature includes two histograms of transaction log flush times to help identify if slow transaction log writes are slowing down server performance. One is of fixed width, and the other has an adaptive width*. These histograms can be viewed in the ctstat utility.
SNAPSHOT_LOGFLUSHTIME_USEC controls the width of the fixed histogram, and the initial width of the adaptive histogram (which defaults to 10 microseconds). This may be changed at server startup by specifying SNAPSHOT_LOGFLUSHTIME_USEC in ctsrvr.cfg. It can also be changed at runtime via ctSETCFG() or the ctadmn utility (select 10. Change Server Settings and then 10. Change the specified configuration option). When the fixed width is changed or the initial adaptive width is automatically adjusted, the histogram box values are reset to zero.
*The first time the server starts, the server sets the adaptive histogram box width to the default value or the SNAPSHOT_LOGFLUSHTIME_USEC value specified in ctsrvr.cfg. As the server runs, on each checkpoint operation, it determines if a significant fraction of the log save values since the last checkpoint are at the low or high end of the histogram range. If so, the server changes the histogram box width to a value that centers the average log save time in the histogram boxes.
