Index: src/main/java/org/apache/jackrabbit/oak/explorer/Explorer.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/explorer/Explorer.java	(revision 1711291)
+++ src/main/java/org/apache/jackrabbit/oak/explorer/Explorer.java	(working copy)
@@ -239,6 +239,15 @@
             }
         });
 
+        JMenuItem menuPCM = new JMenuItem("Persisted Compaction Maps");
+        menuPCM.setMnemonic(KeyEvent.VK_P);
+        menuPCM.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent ev) {
+                treePanel.printPCMInfo();
+            }
+        });
+
         menuBar.add(menuReopen);
         menuBar.add(new JSeparator(JSeparator.VERTICAL));
         menuBar.add(menuCompaction);
@@ -249,6 +258,8 @@
         menuBar.add(new JSeparator(JSeparator.VERTICAL));
         menuBar.add(menuDiff);
         menuBar.add(new JSeparator(JSeparator.VERTICAL));
+        menuBar.add(menuPCM);
+        menuBar.add(new JSeparator(JSeparator.VERTICAL));
 
         frame.setJMenuBar(menuBar);
         frame.pack();
Index: src/main/java/org/apache/jackrabbit/oak/explorer/NodeStoreTree.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/explorer/NodeStoreTree.java	(revision 1711291)
+++ src/main/java/org/apache/jackrabbit/oak/explorer/NodeStoreTree.java	(working copy)
@@ -39,6 +39,7 @@
 import static org.apache.jackrabbit.oak.plugins.segment.FileStoreHelper.newline;
 import static org.apache.jackrabbit.oak.plugins.segment.FileStoreHelper.printGcRoots;
 import static org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStateHelper.getTemplateId;
+import static org.apache.jackrabbit.oak.plugins.segment.SegmentNodeStateHelper.readPCMHistory;
 
 import java.awt.GridLayout;
 import java.io.Closeable;
@@ -64,6 +65,7 @@
 import org.apache.jackrabbit.oak.api.PropertyState;
 import org.apache.jackrabbit.oak.api.Type;
 import org.apache.jackrabbit.oak.plugins.segment.RecordId;
+import org.apache.jackrabbit.oak.plugins.segment.RecordUsageAnalyser;
 import org.apache.jackrabbit.oak.plugins.segment.SegmentBlob;
 import org.apache.jackrabbit.oak.plugins.segment.SegmentId;
 import org.apache.jackrabbit.oak.plugins.segment.SegmentNodeState;
@@ -647,6 +649,37 @@
         return true;
     }
 
+    public void printPCMInfo() {
+        Map<String, Set<Entry<RecordId, RecordId>>> pcms = readPCMHistory(store);
+        if (pcms.isEmpty()) {
+            setText("No persisted compaction map found.");
+            return;
+        }
+        RecordUsageAnalyser rua = new RecordUsageAnalyser();
+
+        StringBuilder sb = new StringBuilder();
+        sb.append("Persisted compaction map info");
+        sb.append(newline);
+        for(Entry<String, Set<Entry<RecordId, RecordId>>> pcm: pcms.entrySet()){
+            sb.append(pcm.getKey());
+            sb.append(" = ");
+            sb.append(pcm.getValue());
+            sb.append(newline);
+            for(Entry<RecordId, RecordId> e: pcm.getValue()){
+                try {
+                    rua.analyseNode(e.getKey());
+                    rua.analyseNode(e.getValue());
+                } catch (IllegalStateException ex) {
+                    ex.printStackTrace();
+                }
+            }
+        }
+        sb.append(newline);
+        sb.append(rua.toString());
+        sb.append(newline);
+        setText(sb.toString());
+    }
+
     private static class NamePathModel implements Comparable<NamePathModel> {
 
         private final FileStore store;
Index: src/main/java/org/apache/jackrabbit/oak/plugins/segment/SegmentNodeStateHelper.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/segment/SegmentNodeStateHelper.java	(revision 1711291)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/segment/SegmentNodeStateHelper.java	(working copy)
@@ -18,6 +18,18 @@
  */
 package org.apache.jackrabbit.oak.plugins.segment;
 
+import static com.google.common.collect.Maps.newHashMap;
+import static com.google.common.collect.Sets.newHashSet;
+import static org.apache.jackrabbit.oak.plugins.segment.PersistedCompactionMap.PERSISTED_COMPACTION_MAP;
+
+import java.util.AbstractMap.SimpleImmutableEntry;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.UUID;
+
+import org.apache.jackrabbit.oak.plugins.segment.file.FileStore;
+
 public class SegmentNodeStateHelper {
 
     private SegmentNodeStateHelper() {
@@ -28,4 +40,84 @@
         return s.getTemplateId();
     }
 
+    public static String readString(RecordId r) {
+        return Segment.readString(r);
+    }
+
+    /**
+     * Extracts persisted compaction map information, if available, otherwise
+     * returs null
+     */
+    public static Entry<RecordId, RecordId> parsePCMInfo(String mapInfo,
+            FileStore store) {
+        if (mapInfo == null || !mapInfo.startsWith(PERSISTED_COMPACTION_MAP)) {
+            return null;
+        }
+        SegmentTracker tracker = store.getTracker();
+        int idStartIndex = mapInfo.indexOf("id=") + 3;
+        int idEndIndex = mapInfo.indexOf(",", idStartIndex);
+        String id = mapInfo.substring(idStartIndex, idEndIndex);
+        RecordId rid = null;
+        try {
+            rid = RecordId.fromString(tracker, id);
+        } catch (IllegalArgumentException iae) {
+            // log a warn?
+        }
+
+        int baseStartIndex = mapInfo.indexOf("baseId=") + 7;
+        String base = mapInfo.substring(baseStartIndex, mapInfo.length() - 1);
+        RecordId bid = null;
+        if (!"null".equals(base)) {
+            try {
+                bid = RecordId.fromString(tracker, base);
+            } catch (IllegalArgumentException iae) {
+                // log a warn?
+            }
+        }
+        return new SimpleImmutableEntry<RecordId, RecordId>(rid, bid);
+    }
+
+    public static Map<String, Set<Entry<RecordId, RecordId>>> readPCMHistory(
+            FileStore store) {
+        Map<String, Set<Entry<RecordId, RecordId>>> pcms = newHashMap();
+        Map<String, Set<UUID>> index = store.getTarReaderIndex();
+        for (String path : index.keySet()) {
+            Set<UUID> segments = index.get(path);
+
+            for (UUID id : segments) {
+                Segment s = store.readSegment(new SegmentId(store.getTracker(),
+                        id.getMostSignificantBits(), id
+                                .getLeastSignificantBits()));
+                if (s.getSegmentId().isBulkSegmentId()) {
+                    continue;
+                }
+
+                for (int r = 0; r < s.getRootCount(); r++) {
+                    RecordType t = s.getRootType(r);
+                    if (t == RecordType.VALUE) {
+                        // ?? s.readRecordId(s.getRootOffset(r));
+                        RecordId nodeId = new RecordId(s.getSegmentId(),
+                                s.getRootOffset(r));
+                        String v = readString(nodeId);
+                        Entry<RecordId, RecordId> pcm = parsePCMInfo(v, store);
+
+                        if (pcm != null) {
+                            Set<Entry<RecordId, RecordId>> pcmsByFile = pcms
+                                    .get(path);
+                            if (pcmsByFile == null) {
+                                pcmsByFile = newHashSet();
+                                pcms.put(path, pcmsByFile);
+                            }
+                            pcmsByFile.add(pcm);
+                            pcmsByFile
+                                    .add(new SimpleImmutableEntry<RecordId, RecordId>(
+                                            nodeId, null));
+                        }
+                    }
+                }
+            }
+        }
+        return pcms;
+    }
+
 }