PER_HIST_ASG_EFFECTIVE_START_DATE DBI is not working in Global absence accrual matrix formula

Summary:

change_contexts (PERSON_ID = l_person_id)

   (

WHILE PER_HIST_ASG_EFFECTIVE_START_DATE.EXISTS(i)

   LOOP

  (i=1+1

))

We have an accrual matrix to the front-loaded absence plan and though the assignment history exists for an employee, it's not going to the loop

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Code Snippet (add any code snippets that support your topic, if applicable):

   change_contexts (PERSON_ID = l_person_id)

   (

   /*get all the assignment start dates*/

   WHILE PER_HIST_ASG_EFFECTIVE_START_DATE.EXISTS(i)

   LOOP

   (   

   /*get the valid records for period and store in a array*/