Java Cloud Service basic (S1) and trial provides 5 DB connections in your connection pool. Make sure that your application is releasing the connections after each requests.
Your application seems to be holding on to the connections and running out of it after 4-5 attempts,
To adjust tuning parameters for ADF BC for cloud, it's recommended to change the following in the AM configuration:
- ensure jbo.txn.disconnect_level =1
- specify "Disconnect upon Release"
Can you please try these.