▁period ▁between ▁the ▁start ▁and ▁the ▁end ▁of ▁a ▁transaction ▁is ▁typically ▁a ▁few ▁seconds ▁or ▁less ). ▁ ▁V MD S ▁supports ▁long ▁transactions ▁in ▁which ▁the ▁volume ▁of ▁data ▁involved ▁in ▁the ▁transaction ▁can ▁be ▁substantial ▁and ▁the ▁duration ▁of ▁the ▁transaction ▁can ▁be ▁significant ▁( days , ▁weeks ▁or ▁even ▁months ). ▁These ▁types ▁of ▁transaction ▁are ▁common ▁in ▁advanced ▁network ▁applications ▁used ▁by , ▁for ▁example , ▁power ▁distribution ▁util ities . ▁ ▁Due ▁to ▁the ▁time ▁span ▁of ▁a ▁long ▁transaction ▁in ▁this ▁context ▁the ▁amount ▁of ▁change ▁can ▁be ▁significant ▁( not ▁only ▁within ▁the ▁scope ▁of ▁the ▁transaction , ▁but ▁also ▁within ▁the ▁context ▁of ▁the ▁database ▁as ▁a ▁whole ). ▁According ly , ▁it ▁is ▁likely ▁that ▁the ▁same ▁record ▁might ▁be ▁changed ▁more ▁than ▁once . ▁To ▁co pe ▁with ▁this ▁scenario ▁V MD S ▁has ▁in built ▁support ▁for ▁automatically ▁man aging ▁such ▁conflicts ▁and ▁allows ▁applications ▁to ▁review ▁changes ▁and ▁accept ▁only ▁those ▁ed its ▁that ▁are ▁correct . ▁ ▁Sp atial ▁and ▁topological ▁capabilities ▁As ▁well ▁as ▁conventional ▁rel ational ▁database ▁features ▁such ▁as ▁attribute ▁query ing , ▁join ▁fields , ▁triggers ▁and ▁calculated ▁fields , ▁V MD S ▁has ▁numerous ▁spatial ▁and ▁topological ▁capabilities . ▁This ▁allows ▁spatial ▁data ▁such ▁as ▁points , ▁texts , ▁pol yl ines , ▁pol yg ons ▁and ▁r aster ▁data ▁to ▁be ▁stored ▁and ▁anal ys ed . ▁ ▁Sp atial ▁functions ▁include : ▁find ▁all ▁features ▁within ▁a ▁polygon , ▁calculate ▁the ▁Vor