Index: dbmod.scm
==================================================================
--- dbmod.scm
+++ dbmod.scm
@@ -208,23 +208,26 @@
     (dbr:dbstruct-dbfname-set!   dbstruct dbfname)
     (dbr:dbstruct-sync-proc-set! dbstruct
 				 (lambda (last-update)
 				   (if *sync-in-progress*
 				       (debug:print 3 *default-log-port* "WARNING: overlapping calls to sync to disk")
-				       (let* ((sync-cmd (conc "megatest -db2db -from "tmpdb" -to "dbfullname"&")))
+				       (let* ((sync-cmd (conc "megatest -db2db -from "tmpdb" -to "dbfullname"&"))
+					      (synclock-file (conc dbfullname".sync-lock")))
 					 ;; (mutex-lock! *db-with-db-mutex*) ;; this mutex is used when overloaded or during a query that modifies the db
-					 (set! *sync-in-progress* #t)
 					 ;; (if (eq? (dbfile:cache-method) 'inmem)
 					 ;;     (dbmod:sync-gasket tables last-update inmem db
 					 ;; 			dbfullname syncdir keys)
-					 (thread-start! (make-thread
-							 (lambda ()
-							   (debug:print-info "Running "sync-cmd)
-							   (system sync-cmd)
-							   ;; (mutex-unlock! *db-with-db-mutex*)
-							   ;; (thread-sleep! 0.5) ;; ensure at least 1/2 second down time between sync calls
-							   (set! *sync-in-progress* #f))))
+					 (if (file-exists? synclock-file)
+					     (debug:print 0 *default-log-port* "Skipping sync, lockfile "synclock-file" found.")
+					     (thread-start! (make-thread
+							     (lambda ()
+							       (set! *sync-in-progress* #t)
+							       (debug:print-info "Running "sync-cmd)
+							       (system sync-cmd)
+							       ;; (mutex-unlock! *db-with-db-mutex*)
+							       ;; (thread-sleep! 0.5) ;; ensure at least 1/2 second down time between sync calls
+							       (set! *sync-in-progress* #f)))))
 					 ))))
     ;; (dbmod:sync-tables tables #f db inmem)
     ;; (if db
     (dbmod:sync-gasket tables #f inmem db dbfullname 'fromdest keys) ;; ) ;; load into inmem
     (dbr:dbstruct-last-update-set! dbstruct (current-seconds)) ;; should this be offset back in time by one second?