How can we retrieve the PIW start date for a period of sickness absence for reporting purposes?

We 're using Oracle EBS 12.2 RUP18 and have been tasked with writing a report to return sickness absence data with statutory and company sick pay entitlements.

We must include the Period of Incapacity (PIW) start date for each absence with a duration of 4 days or more but cannot find the table and column name where it's being stored.

For linked absences we're using the LINKED_ABSENCE_ID to find the PIW start date.

For absences that aren't linked there isn't an equivalent ID. The column PERIOD_OF_INCAPACITY_ID is NULL in table PER_ABSENCE_ATTENDANCES.

We'd prefer not to have to calculate it in the report query.