XDBC memory leaks

I have a business service that actively reads data from a remote Postgres database. OnProcessInput opens a XDBC (actually JDBC) connection, executes an SQL query, fetches several thousand rows, iterates the resultset, and closes the connection. On each iteration I also need to update each source row in the remote database using PreparedStatement.

In other words, in every OnProcessInput call I have a long running SELECT statement and several thousands small UPDATE statements.

The problems I'm facing are:

1. I cannot execute an UPDATE statement via the same connection that was used before to select rows. IRIS raises exceptions of kind " 34 %PreInvoke+1^%Net.Remote.Object.1". Obviously, a separate connection instance is needed for updates.
2. In the Java/.NET world, a database connection is a reusable resource that is managed by a pool. But if I start creating and destroying connections frequently, I see a drop in the performance of UPDATE operations (about 10x):

Method ReadRows()
{
  Set cnn = ##class(%XDBC.Gateway.Connection).GetConnection("postgres")
  Set st = cnn.CreateStatement()
  Set rs = st.ExecuteQuery("select * from my_postgres_table limit 10000")
  While (rs.Next()) {
     Set id = rs.Get("id")
     Do ..UpdateRow(id, "S")
  }
  Do rs.Close()
  Do st.Close()
  Do cnn.Close()
}

/// DOES IRIS LEVERAGE JAVA/JDBC connection pooling?
Method UpdateRow(id as %String, status as %String)
{
   Set cnn = ##class(%XDBC.Gateway.Connection).GetConnection("postgres")
   Set st = cnn.PrepareStatement("update my_postgres_table set status = ? where id = ?")
   ...
   // Set parameters, execute UPDATE
   Do st.Close()
   Do cnn.Close()
   Set cnn = ""
}

3. This approach also results in a rapid increase in memory consumption by the IRIS server. Pretty soon, IRIS eats up all the memory and I have to restart the Language Server.
4. If I create longer-lived connections, the UPDATE performance is much better, but memory leakage still occurs, although not that quickly.

What am I doing wrong? How can I avoid memory leaks while achieving maximum performance for data update operations in the remote database?