Index: oak-core/src/main/java/org/apache/jackrabbit/oak/api/jmx/RepositoryManagementMBean.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/api/jmx/RepositoryManagementMBean.java	(revision 1615896)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/api/jmx/RepositoryManagementMBean.java	(working copy)
@@ -194,4 +194,12 @@
     @Nonnull
     CompositeData getPropertyIndexAsyncReindexStatus();
 
+    /**
+     * Initiate a data store garbage collection operation.
+     *
+     * @param markOnly whether to mark only
+     * @return  the status of the operation right after it was initiated
+     */
+    @Nonnull
+    CompositeData startDataStoreGC(boolean markOnly);
 }
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/management/RepositoryManager.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/management/RepositoryManager.java	(revision 1615896)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/management/RepositoryManager.java	(working copy)
@@ -123,17 +123,22 @@
     }
 
     @Override
-    public CompositeData startDataStoreGC() {
+    public CompositeData startDataStoreGC(final boolean markOnly) {
         return execute(BlobGCMBean.class, new Function<BlobGCMBean, Status>() {
             @Nonnull
             @Override
             public Status apply(BlobGCMBean blobGCService) {
-                return fromCompositeData(blobGCService.startBlobGC());
+                return fromCompositeData(blobGCService.startBlobGC(markOnly));
             }
         }).toCompositeData();
     }
 
     @Override
+    public CompositeData startDataStoreGC() {
+        return startDataStoreGC(false);
+    }
+
+    @Override
     public CompositeData getDataStoreGCStatus() {
         return execute(BlobGCMBean.class, new Function<BlobGCMBean, Status>() {
             @Nonnull
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/blob/BlobGC.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/blob/BlobGC.java	(revision 1615896)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/blob/BlobGC.java	(working copy)
@@ -61,13 +61,13 @@
 
     @Nonnull
     @Override
-    public CompositeData startBlobGC() {
+    public CompositeData startBlobGC(final boolean markOnly) {
         if (gcOp.isDone()) {
             gcOp = newManagementOperation(OP_NAME, new Callable<String>() {
                 @Override
                 public String call() throws Exception {
                     long t0 = nanoTime();
-                    blobGarbageCollector.collectGarbage();
+                    blobGarbageCollector.collectGarbage(markOnly);
                     return "Blob gc completed in " + formatTime(nanoTime() - t0);
                 }
             });
@@ -81,4 +81,10 @@
     public CompositeData getBlobGCStatus() {
         return gcOp.getStatus().toCompositeData();
     }
+
+    @Override
+    @Nonnull
+    public CompositeData startBlobGC() {
+        return startBlobGC(false);
+    }
 }
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/blob/BlobGCMBean.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/blob/BlobGCMBean.java	(revision 1615896)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/blob/BlobGCMBean.java	(working copy)
@@ -48,4 +48,11 @@
     @Nonnull
     CompositeData getBlobGCStatus();
 
+    /**
+     * Initiate a data store garbage collection operation.
+     *
+     * @param markOnly whether to mark only
+     * @return  the status of the operation right after it was initiated
+     */
+    CompositeData startBlobGC(boolean markOnly);
 }