Hi @ll, Re-sending from different address due to original message disappearing. When running BaseX as a server and connecting to it my update statements are successful but when using BaseX from a jar inside the JVM - Database creation works fine - the update statements don't get committed - not visible to other clients or after restart - to the database. Select queries work fine. Code that - no exception - fails is: final String xQueryUpdate = String.format("for $tab in doc('db')//tabs/tab[@id='%s'] return replace node $tab/content with %s", tabId, value); //$NON-NLS-1$ try { synchronized (SESSION) { new ClientQuery(xQueryUpdate, SESSION, SESSION.getOutputStream()).close(); // System.out.println(new XQuery(xQueryUpdate).execute(CONTEXT)); SESSION.notify(); } } catch (final IOException ioex) { ioex.printStackTrace(); } When trying to use XQuery - In comment - I get: org.basex.core.BaseXException: Improper use? Potential bug? Your feedback is welcome: Contact: basex-talk@mailman.uni-konstanz.de<mailto:basex-talk@mailman.uni-konstanz.de> Version: BaseX 7.6 Java: Oracle Corporation, 1.7.0_10-ea OS: Mac OS X, x86_64 Stack Trace: java.nio.channels.OverlappingFileLockException sun.nio.ch.SharedFileLockTable.checkList(FileLockTable.java:255) sun.nio.ch.SharedFileLockTable.add(FileLockTable.java:152) What might be the issue or have I misunderstood something? / Chris