Index: oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/SegmentBufferWriter.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/SegmentBufferWriter.java	(revision 2c44516ab81e15f4bff3c514677cf25bd269d8ad)
+++ oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/SegmentBufferWriter.java	(revision )
@@ -272,10 +272,11 @@
      */
     public void writeRecordId(RecordId recordId, boolean reference) {
         checkNotNull(recordId);
-
+        checkState(segmentReferences.size() + 1 < 0xffff,
+                "Segment cannot have more than 0xffff references");
         checkGCGeneration(recordId.getSegmentId());
 
-        writeInt(writeSegmentIdReference(recordId.getSegmentId()));
+        writeShort(toShort(writeSegmentIdReference(recordId.getSegmentId())));
         writeInt(recordId.getRecordNumber());
 
         statistics.recordIdCount++;
@@ -283,6 +284,10 @@
         dirty = true;
     }
 
+    private static short toShort(int value) {
+        return (short) value;
+    }
+
     private int writeSegmentIdReference(SegmentId id) {
         if (id.equals(segment.getSegmentId())) {
             return 0;
Index: oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/Segment.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/Segment.java	(revision 2c44516ab81e15f4bff3c514677cf25bd269d8ad)
+++ oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/Segment.java	(revision )
@@ -76,11 +76,11 @@
     static final int RECORD_SIZE = 9;
 
     /**
-     * Number of bytes used for storing a record identifier. One byte
-     * is used for identifying the segment and two for the record offset
+     * Number of bytes used for storing a record identifier. Two bytes
+     * are used for identifying the segment and four for the record offset
      * within that segment.
      */
-    static final int RECORD_ID_BYTES = 4 + 4;
+    static final int RECORD_ID_BYTES = 2 + 4;
 
     /**
      * The limit on segment references within one segment. Since record
@@ -245,6 +245,9 @@
     }
 
     private SegmentReferences readReferencedSegments() {
+        checkState(getReferencedSegmentIdCount() + 1 < 0xffff,
+                "Segment cannot have more than 0xffff references");
+
         List<SegmentId> referencedSegments = newArrayListWithCapacity(getReferencedSegmentIdCount());
 
         int position = data.position();
@@ -444,8 +447,12 @@
     }
 
     private RecordId internalReadRecordId(int pos) {
-        SegmentId segmentId = dereferenceSegmentId(data.getInt(pos));
-        return new RecordId(segmentId, data.getInt(pos + 4));
+        SegmentId segmentId = dereferenceSegmentId(asUnsigned(data.getShort(pos)));
+        return new RecordId(segmentId, data.getInt(pos + 2));
+    }
+
+    private static int asUnsigned(short value) {
+        return value & 0xffff;
     }
 
     private SegmentId dereferenceSegmentId(int reference) {