Error connecting to Oracle via Direct tab: "System.Exception, NET: Unknown error 1" (4228475)

Attempting to connect to an Oracle database directly via Direct tab results in the following error: 

System.Exception: NET: Unknown error 1

Stack trace:
   at CoreLab.Oracle.bk.b(Int32 A_0)
   at CoreLab.Oracle.o.b()
   at CoreLab.Oracle.d.a(Int32 A_0, bu A_1)
   at CoreLab.Oracle.OracleCommand.a(CommandBehavior A_0, IDisposable A_1, Int32 A_2, Int32 A_3)
   at CoreLab.Common.DbCommandBase.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.ExecuteReader()
   at CoreLab.Oracle.OracleCommand.ExecuteNonQuery()
   at CoreLab.Oracle.OracleTransaction..ctor(OracleConnection A_0, IsolationLevel A_1)
   at CoreLab.Oracle.OracleConnection.BeginTransaction(IsolationLevel iso)
   at CoreLab.Oracle.OracleConnection.BeginTransaction()