ASO formula member low performance

Summary

A good performing ASO formula started performing poorly

Content

Hi all,

Our client has an ASO cube that uses a View dimension, like this:

View
    YTD
    Per

Data is loaded into YTD and Per is a never share member with the following formula to calculate periodic (monthly) data:

CASE
WHEN Is(Periodo.CurrentMember,[Jun]) THEN
([YTD],[Jun])-([YTD],[May])
WHEN Is(Periodo.CurrentMember,[May]) THEN
([YTD],[May])-([YTD],[Apr])
WHEN Is(Periodo.CurrentMember,[Apr]) THEN
([YTD],[Apr])-([YTD],[Mar])
WHEN Is(Periodo.CurrentMember,[Mar]) THEN
([YTD],[Mar])-([YTD],[Feb])
WHEN Is(Periodo.CurrentMember,[Feb]) THEN
([YTD],[Feb])-([YTD],[Jan])
WHEN Is(Periodo.CurrentMember,[Jan]) THEN
([YTD],[Jan])-([YTD],[Dec])
WHEN Is(Periodo.CurrentMember,[Dec]) THEN
([YTD],[Dec])-([YTD],[Nov])
WHEN Is(Periodo.CurrentMember,[Nov]) THEN
([YTD],[Nov])-([YTD],[Oct])
WHEN Is(Periodo.CurrentMember,[Oct]) THEN
([YTD],[Oct])-([YTD],[Sep])
WHEN Is(Periodo.CurrentMember,[Sep]) THEN
([YTD],[Sep])-([YTD],[Aug])
WHEN Is(Periodo.CurrentMember,[Aug]) THEN
([YTD],[Aug])-([YTD],[Jul])
ELSE
([YTD],[Jul])
END