AR_INVOICE_API_PUB.CREATE_SINGLE_INVOICE takes long time to complete after DB Restart

Hello,

We have a custom REST web service for creating AR Invoices. We have observed that the first time we call this service after database restart the api ar_invoice_api_pub.create_single_invoice takes approx. 20 sec to complete, however, the later services calls hardly take between 1-2 seconds to complete.

We tried pinning the api package and the corresponding packages it calls in memory, however, that has not helped.

Finally we have taken debug log for the 20 sec run and 2 sec run and compared the debug. The api performs exactly the same steps both the times, however, takes longer to complete the first time it is called.