Specifications

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Chapter 18 Setting Up and Monitoring Performance Statistics and Resource Maps
Using Collection Levels Effectively
 Toretrievemoredetailedmetricsforashortperiodoftime,viewareal‐timedata
chartratherthanincreasethecollectionlevel.Viewingreal‐timedatahasless
impactonperformancebecausemetricsareretrieveddirectlyfromthesource
withoutbeingwrittentotheVirtualCenterdatabase.Formoreinformationon
data
charts,see“PerformanceCharts”onpage 289.
 Whenyouusecollectionlevel3or4todiagnoseproblems,resetthecollectionlevel
toitspreviousstateassoonaspossible.
 Whenyouusecollectionlevel4,trytolimitthecollectionperiodtotheDay
intervalsothedatabaseisn’timpacted.Ifyouneedtosavethedataforlongerthan
1day,increasetheDayintervaldurationto2or3ratherthanusetheWeek
interval.Forexample,
ifyouneedtorecorddataovertheweekend,settheinterval
to3days.Asarule,increasethecollectionintervaltotheWeekintervalonlywhen
youneedtheintervaldurationtobemorethan3days.
How statistical data is stored in the database
Thestatisticaldataforeachcollectionintervalisstoredinitsowndatabasetable.Atthe
endofaninterval,oneoftwothingscanoccur:
 Ifthenextintervalisdisabled,thedatainthetablethatisolderthantheinterval
durationispurged.
 Ifthenextintervalisenabled,thedataisaggregatedintogroupsandisrolledupto
thedatabasetableofthesubsequentcollectioninterval.Forexample,saytheDay
intervalhasa5minutecollectionfrequencyandtheWeekintervalhasa30minute
collectionfrequency.WhentheDay
intervalcompletes,itaggregatesthe5minute
queriesintogroupsof6(equalling30minutes)androllsthe30minutedatablock
totheWeekintervaldatabasetable.Theday‐olddataisthenpurgedfromthe
databasetomakeroomfornewqueries.Figure 18‐1,“Example:DailyStatistics
Collection,”on
page 282showsthedefaultrollupprocess.