src/Pure/Thy/store.scala

 
   def clean_session_info(db: SQL.Database, name: String): Boolean = {
     Export.clean_session(db, name)
     Document_Build.clean_session(db, name)
 
-    Store.Data.transaction_lock(db,
-      create = true,
-      synchronized = true,
-      label = "Store.clean_session_info"
-    ) {
+    Store.Data.transaction_lock(db, create = true, label = "Store.clean_session_info") {
       val already_defined = session_info_defined(db, name)
 
       db.execute_statement(
         Store.Data.Session_Info.table.delete(
           sql = Store.Data.Session_Info.session_name.where_equal(name)))

     session_name: String,
     sources: Store.Sources,
     build_log: Build_Log.Session_Info,
     build: Store.Build_Info
   ): Unit = {
-    Store.Data.transaction_lock(db, synchronized = true, label = "Store.write_session_info") {
+    Store.Data.transaction_lock(db, label = "Store.write_session_info") {
       Store.Data.write_sources(db, session_name, sources)
       Store.Data.write_session_info(db, cache.compress, session_name, build_log, build)
     }
   }