OracleDataAdapter with GlobalTemporaryTable: FillSchema not working - sql

Question

I'm using FillSchema on a OracleDataAdapter in .net. The SelectCommand works on a global temporary table.
For the first run, this works great. I will get the schema of the global temporary table
Then I drop that temporary table and great a new temporary table with a different schema.
After that, for the second run, the FillSchema method will still return the schema from the old dropped temporary table.
Am I missing something? Shouldn't the select command query the schema from the new version of the temp table?
Thanks for any help!

Answer 1

What did not work:
The OracleDataAdapter.SelectCommand that was used by
FillSchema was:
Select * from TableName
What works:
I needed to change that query to the exact schema,
then it works:
Select column1,column2,column3 from TableName
I don't understand exactly why, but that solved my problem.
It will return the schema of the new global temporary table.
Is this a caching problem of the oracle server? Because the
tableName is always the same?

Answer 2

To use procedure ways to solve this Problem
OracleParameter inputParam = new OracleParameter("TABLE_NAME_IN",OracleDbType.Varchar2,"TEST",ParameterDirection.Input); //Query TableName
OracleParameter refParam = new OracleParameter("OUTPUT",OracleDbType.RefCursor,ParameterDirection.Output);//RefCursor
DataTable dt = new DataTable();//Fill DataTable
using (OracleCommand dbCommand = new OracleCommand("PKG_SYS.SELECT_TABLE_DATA",orclConnection))
{
dbCommand.CommandType = CommandType.StoredProcedure;
dbCommand.Parameters.Add(inputParam);
dbCommand.Parameters.Add(refParam);
using (OracleDataAdapter da = new OracleDataAdapter())
{
da.SelectCommand = dbCommand;
da.Fill(dt);
}
}