Transaction slowness

We are facing a weird slowness in database response to users. The situation is - Warehouse operators are unloading trucks on the dock and moving material to locators. When they are doing the activity, they have to scan barcodes on a mobile device and keep moving items in locators to clean up the dock to make a way for another truck for unloading material. When the user is doing the first transaction on a mobile device, it takes 5-10 minutes, but the next transactions are complete in 5-10 seconds. The delay in first transaction completion is causing an overall delay in warehouse work efficiency.

10046 traces enabled on the session while doing the first transaction, which takes 5-10 minutes, revealed that over 80% of the time is going in SQL*NET message from the client. Trace for the next sessions also shows the same event is top, but the transaction completes within 10 seconds.

We don’t understand why the first transaction is taking time, and the next is not so struggling to fix the issue. We also don’t want to conclude it as a network issue because subsequent transactions are quick.

We would appreciate it if any of you could please tell us if anyone has observed the same situation and what we can do to rectify such behavior?

Thank you in advance for your inputs.

Best Regards,
AMIT