Hi, We are having a problem, for a while, that is difficult to isolate. Our ETL includes the following steps: 1) Open JDBC connection, add data to a table, commit, close connection 2) Open JDBC connection, some ALTER TALBLE statements, commit, close connection Occasionally, we get the following during step 2) : java.sql.SQLException: ALTER TABLE: set READ or INSERT ONLY not possible with outstanding updates (wait until updates are flushed) at nl.cwi.monetdb.jdbc.MonetConnection$ResponseList.executeQuery(MonetConnection.java:2732) What puzzles me is that step one is completed when this happens, the commit is done and the connection is closed (we triple-checked that is actually is closed). Notice that inserting a sleep between the to steps makes it work correctly. As I said, this is hard to isolate and reproduce. Still, can anyone guess what is exactly happening? Can it be that a background process is still flushing updates from step 1) ? Even if the JDBC connection is closed ? Can we force a blocking flush, so that it doesn't return until it's safe? If not, how can we know when updates are flushed? Thanks, Roberto