Interleaved executeQuery() generates SQLException: Closed Statement

Question

When i run the following code i see the cats_stmt.executeQuery() line throw a "SQLException: Closed Statement.".
Since I just created the cats_stmt statement - why could it be closed?
The memory_stmt.executeQuery runs without exception.
memory_stmt = connection.prepareStatement(memory_sql,
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
cats_stmt = connection.prepareStatement(cats_sql,
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
index = 1;
memory_stmt.setString(index++, host);
memory_stmt.setString(index++, jvm);
memory_stmt.setLong(index++, starttime);
memory_stmt.setLong(index++, endtime);
memory_rs = memory_stmt.executeQuery();
index = 1;
cats_stmt.setString(index++, host);
cats_stmt.setString(index++, jvm);
cats_stmt.setLong(index++, starttime);
cats_stmt.setLong(index++, endtime);
cats_rs = cats_stmt.executeQuery(); <<- throws exception.
On JDK1.3.1 and Oracle 817
E.g.
java.sql.SQLException: Closed Statement
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:180)
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:222)
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:285)
at oracle.jdbc.driver.OracleStatement.ensureOpen(OracleStatement.java:5681)
at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:409)
at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:366)

Answer 1

I had a hunch that this was a limitation or bug in the driver or pool. I also read in forums that the connection "manages" each Statement it prepares or creates; like it adds it to a List and such ; it also cleans the slate each time the connection is closed.
This code example above is just a small snippit that summarizes over a long time range of data (like days) - that is potentially 1000s of statements and queries and result sets.
It is probably not very common that with jdbc someone prepares and executes 1000s of queries on the same connection over a course of 2 - 10 minutes (that's how long the entire operationcould take). I guessed the connection was worn out and tired .
I changed the code to get a connection and then close the connection periodically - instead of getting one connection and using it for the whole period. After that all these hard to explain Closed Statement exceptions disappeared.
i think the interleaving queries is OK. I guess the connection was blowing out.