The cause is worng permissions provided to teh Database user.
The permissions should be RESOURCE and CONNECT only and not any other permission.
Adding more permissions will cause the deployment to fail.
This is specified in the documentation (in teh Virtual Appliance Web UI -> help -> Prerequisites for configuring the vApp with an external database), and also on the same page where you configure the database credentials during setup)
a. Create an Identity Portal database.
b. Create a user with CONNECT and RESOURCE privileges on the Identity Portal database.