If you write an Xtender to extend the payments window in Service Central (for example), and you need the TRANS_NUMBER, this code won't return the value:

Dim strTrans As String
RaiseEvent GetValue("IMISSC^Trans.TRANS_NUMBER", strTrans)

...but this code will:

Dim strTrans As String
RaiseEvent GetValue("IMISAR^Trans.TRANS_NUMBER", strTrans)

iMISAR contains core financials code for iMIS, and it's shared by other modules. In general, if you're looking for financial data for an Xtender, and can't find it in the current library, try IMISAR instead.