@Override
    public VersionTag generateVersionTag(VersionSource member, boolean withDelta,
        InternalRegion region, EntryEventImpl event) {
      return null;
    }
Adds any live entries in this list to liveEntries and returns the index of the next free
slot.

@param liveEntries the array to fill with the live entries
@param idx the first free slot in liveEntries
@param drv the disk region these entries are on
@return the next free slot in liveEntries
geode-core/src/main/java/org/apache/geode/internal/cache/Oplog.java