Creating Analysis Services Cubes - SQL Server Analysis Services 2012 Cube Development - page 120

build aggregations "lazily" using a background thread. The term "lazy" indicates that
the thread uses minimal resources and works only when sufficient system resources
are available.
Therefore, building aggregations lazily could take considerably longer than through
ProcessIndexes . The configuration property that controls whether the lazy thread
is activated is OLAP\LazyProcessing\Enabled —the default value is 1 , which
means the lazy thread is active. If you prefer not to have the lazy thread building
missing aggregations or indexes, set the property to 0 . You must also set the Pro-
cessingMode property on the cube, measure group, or partition level to customize
data availability.