Database Item names for Assignment DFF segment values

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Database Item for Assignment DFF segment values

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What's the DBI name I need to reference Assignment DFF segment values, in formula type Oracle Payroll. I can't find the correct Database Item name. The column name is ****_ATTRIBUTE_DATE1, the flexfield code is PER_ASG_DF. 

I've tried using these two DBIs but they are not giving me the segment value:

PER_EXT_ASG_BASIC_HIST_****_ATTRIBUTE_DATE1 and

PER_ASG_INFORMATION_DATE1

I am aware i may need to use a Payroll Access to HR formula type to get the DBI value. 

Thanks