oops

h2/src/main/org/h2/mvstore/tx/TransactionStore.java

@@ -144,12 +144,16 @@ public class TransactionStore {
         if (!init) {
             for (String mapName : store.getMapNames()) {
                 if (mapName.startsWith(UNDO_LOG_NAME_PREFIX)) {
+                    // The following block will be executed only once
+                    // upon upgrade from older version where
+                    // undo log was persisted as a single map
                     if (mapName.equals(UNDO_LOG_NAME_PREFIX)) {
-                        if (!store.hasData(mapName) || store.isReadOnly()) {
+                        if (!store.hasData(mapName) && !store.isReadOnly()) {
                             store.removeMap(mapName);
                         }
                         continue;
                     }
+
                     boolean committed = mapName.charAt(UNDO_LOG_NAME_PREFIX.length()) == UNDO_LOG_COMMITTED;
                     if (store.hasData(mapName) || committed) {
                         int transactionId = Integer.parseInt(mapName.substring(UNDO_LOG_NAME_PREFIX.length() + 1));