diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index d283fc3..0c74d53 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -1,3 +1,14 @@
+version 0.7.12
+--------------
+
+- minor bug fixes: 2 in JSON RPC, 1 in get_utxos (affected addresslistunspent)
+- leveldb / rocksdb are opened with a different maximum open files limit,
+  depending on whether the chain has been fully synced or not.  If synced
+  you want the files for network sockets, if not synced for the DB engines.
+  Once synced the DB will be reopened with the lower limit to free up the
+  files for serving network connections
+- various refactoring preparing for possible asynchronous block processing
+
 version 0.7.11
 --------------
 
diff --git a/lib/jsonrpc.py b/lib/jsonrpc.py
index ee416e0..23bcd93 100644
--- a/lib/jsonrpc.py
+++ b/lib/jsonrpc.py
@@ -277,7 +277,7 @@ class JSONRPC(asyncio.Protocol, LoggedClass):
         except RCPError:
             pass
         else:
-            self.handle_notification(method, params)
+            await self.handle_notification(method, params)
         return None
 
     async def json_request(self, message):
@@ -297,7 +297,7 @@ class JSONRPC(asyncio.Protocol, LoggedClass):
             await self.handle_response(message['result'], None, message['id'])
         return None
 
-    def raise_unknown_method(method):
+    def raise_unknown_method(self, method):
         '''Respond to a request with an unknown method.'''
         raise self.RPCError('unknown method: "{}"'.format(method),
                             self.METHOD_NOT_FOUND)
diff --git a/server/block_processor.py b/server/block_processor.py
index a1619cb..1e661ac 100644
--- a/server/block_processor.py
+++ b/server/block_processor.py
@@ -23,24 +23,22 @@ from lib.util import chunks, formatted_time, LoggedClass
 import server.db
 
 
-class ChainError(Exception):
-    pass
-
-
 class Prefetcher(LoggedClass):
     '''Prefetches blocks (in the forward direction only).'''
 
-    def __init__(self, daemon, height):
+    def __init__(self, tasks, daemon, height):
         super().__init__()
+        self.tasks = tasks
         self.daemon = daemon
         self.semaphore = asyncio.Semaphore()
-        self.queue = asyncio.Queue()
-        self.queue_size = 0
         self.caught_up = False
         self.fetched_height = height
+        # A list of (blocks, size) pairs.  Earliest last.
+        self.cache = []
+        self.cache_size = 0
         # Target cache size.  Has little effect on sync time.
         self.target_cache_size = 10 * 1024 * 1024
-        # First fetch to be 10 blocks
+        # This makes the first fetch be 10 blocks
         self.ave_size = self.target_cache_size // 10
 
     async def clear(self, height):
@@ -53,19 +51,19 @@ class Prefetcher(LoggedClass):
         with await self.semaphore:
             while not self.queue.empty():
                 self.queue.get_nowait()
-            self.queue_size = 0
+            self.cache = []
+            self.cache_size = 0
             self.fetched_height = height
-            self.caught_up = False
+            self.logger.info('reset to height'.format(height))
 
-    async def get_blocks(self):
-        '''Blocking function that returns prefetched blocks.
-
-        The returned result empty just once - when the prefetcher
-        has caught up with the daemon.
-        '''
-        blocks, size = await self.queue.get()
-        self.queue_size -= size
-        return blocks
+    def get_blocks(self):
+        '''Return the next list of blocks from our prefetch cache.'''
+        # Cache might be empty after a clear()
+        if self.cache:
+            blocks, size = self.cache.pop()
+            self.cache_size -= size
+            return blocks
+        return []
 
     async def main_loop(self):
         '''Loop forever polling for more blocks.'''
@@ -73,9 +71,13 @@ class Prefetcher(LoggedClass):
                          .format(await self.daemon.height()))
         while True:
             try:
-                with await self.semaphore:
-                    await self._prefetch()
-                await asyncio.sleep(5 if self.caught_up else 0)
+                secs = 0
+                if self.cache_size < self.target_cache_size:
+                    if not await self._prefetch():
+                        self.caught_up = True
+                        secs = 5
+                    self.tasks.put_nowait(None)
+                await asyncio.sleep(secs)
             except DaemonError as e:
                 self.logger.info('ignoring daemon error: {}'.format(e))
             except asyncio.CancelledError:
@@ -83,41 +85,41 @@ class Prefetcher(LoggedClass):
 
     async def _prefetch(self):
         '''Prefetch blocks unless the prefetch queue is full.'''
-        if self.queue_size >= self.target_cache_size:
-            return
-
         daemon_height = await self.daemon.height()
         cache_room = self.target_cache_size // self.ave_size
 
-        # Try and catch up all blocks but limit to room in cache.
-        # Constrain count to between 0 and 4000 regardless
-        count = min(daemon_height - self.fetched_height, cache_room)
-        count = min(4000, max(count, 0))
-        if not count:
-            # Indicate when we have caught up for the first time only
-            if not self.caught_up:
-                self.caught_up = True
-                self.queue.put_nowait(([], 0))
-            return
+        with await self.semaphore:
+            # Try and catch up all blocks but limit to room in cache.
+            # Constrain count to between 0 and 4000 regardless
+            count = min(daemon_height - self.fetched_height, cache_room)
+            count = min(4000, max(count, 0))
+            if not count:
+                return 0
 
-        first = self.fetched_height + 1
-        hex_hashes = await self.daemon.block_hex_hashes(first, count)
-        if self.caught_up:
-            self.logger.info('new block height {:,d} hash {}'
-                             .format(first + count - 1, hex_hashes[-1]))
-        blocks = await self.daemon.raw_blocks(hex_hashes)
-        size = sum(len(block) for block in blocks)
+            first = self.fetched_height + 1
+            hex_hashes = await self.daemon.block_hex_hashes(first, count)
+            if self.caught_up:
+                self.logger.info('new block height {:,d} hash {}'
+                                 .format(first + count - 1, hex_hashes[-1]))
+            blocks = await self.daemon.raw_blocks(hex_hashes)
 
-        # Update our recent average block size estimate
-        if count >= 10:
-            self.ave_size = size // count
-        else:
-            self.ave_size = (size + (10 - count) * self.ave_size) // 10
+            size = sum(len(block) for block in blocks)
 
-        self.fetched_height += len(blocks)
-        self.queue.put_nowait((blocks, size))
-        self.queue_size += size
+            # Update our recent average block size estimate
+            if count >= 10:
+                self.ave_size = size // count
+            else:
+                self.ave_size = (size + (10 - count) * self.ave_size) // 10
 
+            self.cache.insert(0, (blocks, size))
+            self.cache_size += size
+            self.fetched_height += len(blocks)
+
+            return count
+
+
+class ChainError(Exception):
+    '''Raised on error processing blocks.'''
 
 class ChainReorg(Exception):
     '''Raised on a blockchain reorganisation.'''
@@ -135,6 +137,9 @@ class BlockProcessor(server.db.DB):
 
         self.client = client
 
+        # The block processor reads its tasks from this queue
+        self.tasks = asyncio.Queue()
+
         # These are our state as we move ahead of DB state
         self.fs_height = self.db_height
         self.fs_tx_count = self.db_tx_count
@@ -144,6 +149,7 @@ class BlockProcessor(server.db.DB):
 
         self.daemon = Daemon(self.coin.daemon_urls(env.daemon_url))
         self.caught_up = False
+        self._shutdown = False
         self.event = asyncio.Event()
 
         # Meta
@@ -154,7 +160,7 @@ class BlockProcessor(server.db.DB):
         # Headers and tx_hashes have one entry per block
         self.history = defaultdict(partial(array.array, 'I'))
         self.history_size = 0
-        self.prefetcher = Prefetcher(self.daemon, self.height)
+        self.prefetcher = Prefetcher(self.tasks, self.daemon, self.height)
 
         self.last_flush = time.time()
         self.last_flush_tx_count = self.tx_count
@@ -176,33 +182,33 @@ class BlockProcessor(server.db.DB):
 
     async def main_loop(self):
         '''Main loop for block processing.'''
-        try:
-            # Simulate a reorg if requested
-            if self.env.force_reorg > 0:
-                self.logger.info('DEBUG: simulating reorg of {:,d} blocks'
-                                 .format(self.env.force_reorg))
-                await self.handle_chain_reorg(self.env.force_reorg, set())
 
-            while True:
-                await self._wait_for_update()
-        except asyncio.CancelledError:
-            pass
+        # Simulate a reorg if requested
+        if self.env.force_reorg > 0:
+            self.logger.info('DEBUG: simulating reorg of {:,d} blocks'
+                             .format(self.env.force_reorg))
+            await self.handle_chain_reorg(set(), self.env.force_reorg)
+
+        while True:
+            task = await self.tasks.get()
+            if self._shutdown:
+                break
+            blocks = self.prefetcher.get_blocks()
+            if blocks:
+                await self.advance_blocks(blocks)
+            elif not self.caught_up:
+                self.caught_up = True
+                self.first_caught_up()
 
-    async def shutdown(self):
-        '''Shut down the DB cleanly.'''
-        self.logger.info('flushing state to DB for clean shutdown...')
         self.flush(True)
 
-    async def _wait_for_update(self):
-        '''Wait for the prefetcher to deliver blocks.
-
-        Blocks are only processed in the forward direction.
-        '''
-        blocks = await self.prefetcher.get_blocks()
-        if not blocks:
-            self.first_caught_up()
-            return
+    def shutdown(self):
+        '''Call to shut down the block processor.'''
+        self.logger.info('flushing state to DB for clean shutdown...')
+        self._shutdown = True
+        self.tasks.put_nowait(None)
 
+    async def advance_blocks(self, blocks):
         '''Strip the unspendable genesis coinbase.'''
         if self.height == -1:
             blocks[0] = blocks[0][:self.coin.HEADER_LEN] + bytes(1)
@@ -213,11 +219,12 @@ class BlockProcessor(server.db.DB):
                 self.advance_block(block, touched)
                 await asyncio.sleep(0)  # Yield
         except ChainReorg:
-            await self.handle_chain_reorg(None, touched)
+            await self.handle_chain_reorg(touched)
 
         if self.caught_up:
             # Flush everything as queries are performed on the DB and
             # not in-memory.
+            await asyncio.sleep(0)
             self.flush(True)
             self.client.notify(touched)
         elif time.time() > self.next_cache_check:
@@ -225,23 +232,23 @@ class BlockProcessor(server.db.DB):
             self.next_cache_check = time.time() + 60
 
     def first_caught_up(self):
-        '''Called when first caught up after start, or after a reorg.'''
-        self.caught_up = True
-        if self.first_sync:
-            self.first_sync = False
-            self.logger.info('{} synced to height {:,d}.  DB version:'
-                             .format(VERSION, self.height, self.db_version))
+        '''Called when first caught up after starting.'''
         self.flush(True)
+        if self.first_sync:
+            self.logger.info('{} synced to height {:,d}'
+                             .format(VERSION, self.height))
+            self.first_sync = False
+            self.flush_state(self.db)
+            self.reopen_db(False)
         self.event.set()
 
-    async def handle_chain_reorg(self, count, touched):
+    async def handle_chain_reorg(self, touched, count=None):
         '''Handle a chain reorganisation.
 
         Count is the number of blocks to simulate a reorg, or None for
         a real reorg.'''
         self.logger.info('chain reorg detected')
         self.flush(True)
-        self.logger.info('finding common height...')
 
         hashes = await self.reorg_hashes(count)
         # Reverse and convert to hex strings.
@@ -251,7 +258,6 @@ class BlockProcessor(server.db.DB):
             self.backup_blocks(blocks, touched)
 
         await self.prefetcher.clear(self.height)
-        self.logger.info('prefetcher reset')
 
     async def reorg_hashes(self, count):
         '''Return the list of hashes to back up beacuse of a reorg.
@@ -305,12 +311,11 @@ class BlockProcessor(server.db.DB):
         assert not self.utxo_cache
         assert not self.db_deletes
 
-    def flush(self, flush_utxos=False, flush_history=None):
+    def flush(self, flush_utxos=False):
         '''Flush out cached state.
 
         History is always flushed.  UTXOs are flushed if flush_utxos.'''
         if self.height == self.db_height:
-            assert flush_history is None
             self.assert_flushed()
             return
 
@@ -319,14 +324,10 @@ class BlockProcessor(server.db.DB):
         last_flush = self.last_flush
         tx_diff = self.tx_count - self.last_flush_tx_count
 
-        if self.height > self.db_height:
-            assert flush_history is None
-            flush_history = self.flush_history
-
         with self.db.write_batch() as batch:
             # History first - fast and frees memory.  Flush state last
             # as it reads the wall time.
-            flush_history(batch)
+            self.flush_history(batch)
             if flush_utxos:
                 self.flush_utxos(batch)
             self.flush_state(batch)
@@ -394,12 +395,36 @@ class BlockProcessor(server.db.DB):
         self.tx_hashes = []
         self.headers = []
 
-    def backup_history(self, batch, hash168s):
-        self.logger.info('backing up history to height {:,d}  tx_count {:,d}'
-                         .format(self.height, self.tx_count))
+    def backup_flush(self, hash168s):
+        '''Like flush() but when backing up.  All UTXOs are flushed.
 
+        hash168s - sequence of hash168s which were touched by backing
+        up.  Searched for history entries to remove after the backup
+        height.
+        '''
+        assert self.height < self.db_height
         assert not self.history
 
+        self.flush_count += 1
+        flush_start = time.time()
+
+        with self.db.write_batch() as batch:
+            # Flush state last as it reads the wall time.
+            self.backup_history(batch, hash168s)
+            self.flush_utxos(batch)
+            self.flush_state(batch)
+
+        # Update and put the wall time again - otherwise we drop the
+        # time it took to commit the batch
+        self.flush_state(self.db)
+
+        self.logger.info('backup flush #{:,d} took {:.1f}s.  '
+                         'Height {:,d} txs: {:,d}'
+                         .format(self.flush_count,
+                                 self.last_flush - flush_start,
+                                 self.height, self.tx_count))
+
+    def backup_history(self, batch, hash168s):
         nremoves = 0
         for hash168 in sorted(hash168s):
             prefix = b'H' + hash168
@@ -426,8 +451,8 @@ class BlockProcessor(server.db.DB):
         assert not self.headers
         assert not self.tx_hashes
 
-        self.logger.info('removed {:,d} history entries from {:,d} addresses'
-                         .format(nremoves, len(hash168s)))
+        self.logger.info('backing up removed {:,d} history entries from '
+                         '{:,d} addresses'.format(nremoves, len(hash168s)))
 
     def check_cache_size(self):
         '''Flush a cache if it gets too big.'''
@@ -462,9 +487,6 @@ class BlockProcessor(server.db.DB):
         self.tx_counts.append(prior_tx_count + len(txs))
 
     def advance_block(self, block, touched):
-        # We must update the FS cache before calling advance_txs() as
-        # the UTXO cache uses the FS cache via get_tx_hash() to
-        # resolve compressed key collisions
         header, tx_hashes, txs = self.coin.read_block(block)
         if self.tip != self.coin.header_prevhash(header):
             raise ChainReorg
@@ -477,43 +499,47 @@ class BlockProcessor(server.db.DB):
             self.write_undo_info(self.height, b''.join(undo_info))
 
     def advance_txs(self, tx_hashes, txs, touched):
-        put_utxo = self.utxo_cache.__setitem__
-        spend_utxo = self.spend_utxo
         undo_info = []
 
         # Use local vars for speed in the loops
         history = self.history
+        history_size = self.history_size
         tx_num = self.tx_count
         script_hash168 = self.coin.hash168_from_script()
         s_pack = pack
+        put_utxo = self.utxo_cache.__setitem__
+        spend_utxo = self.spend_utxo
+        undo_info_append = undo_info.append
 
         for tx, tx_hash in zip(txs, tx_hashes):
             hash168s = set()
+            add_hash168 = hash168s.add
             tx_numb = s_pack('<I', tx_num)
 
             # Spend the inputs
             if not tx.is_coinbase:
                 for txin in tx.inputs:
                     cache_value = spend_utxo(txin.prev_hash, txin.prev_idx)
-                    undo_info.append(cache_value)
-                    hash168s.add(cache_value[:21])
+                    undo_info_append(cache_value)
+                    add_hash168(cache_value[:21])
 
             # Add the new UTXOs
             for idx, txout in enumerate(tx.outputs):
                 # Get the hash168.  Ignore unspendable outputs
                 hash168 = script_hash168(txout.pk_script)
                 if hash168:
-                    hash168s.add(hash168)
+                    add_hash168(hash168)
                     put_utxo(tx_hash + s_pack('<H', idx),
                              hash168 + tx_numb + s_pack('<Q', txout.value))
 
             for hash168 in hash168s:
                 history[hash168].append(tx_num)
-            self.history_size += len(hash168s)
+            history_size += len(hash168s)
             touched.update(hash168s)
             tx_num += 1
 
         self.tx_count = tx_num
+        self.history_size = history_size
 
         return undo_info
 
@@ -523,7 +549,6 @@ class BlockProcessor(server.db.DB):
         The blocks should be in order of decreasing height.
         A flush is performed once the blocks are backed up.
         '''
-        self.logger.info('backing up {:,d} blocks'.format(len(blocks)))
         self.assert_flushed()
 
         for block in blocks:
@@ -544,8 +569,7 @@ class BlockProcessor(server.db.DB):
 
         # touched includes those passed into this function.  That will
         # generally be empty but is harmless if not.
-        flush_history = partial(self.backup_history, hash168s=touched)
-        self.flush(True, flush_history=flush_history)
+        self.backup_flush(touched)
 
     def backup_txs(self, tx_hashes, txs, touched):
         # Prevout values, in order down the block (coinbase first if present)
@@ -665,8 +689,9 @@ class BlockProcessor(server.db.DB):
 
             if len(candidates) > 1:
                 tx_num, = unpack('<I', tx_num_packed)
-                hash, height = self.get_tx_hash(tx_num)
+                hash, height = self.fs_tx_hash(tx_num)
                 if hash != tx_hash:
+                    assert hash is not None  # Should always be found
                     continue
 
             # Key: b'u' + address_hash168 + tx_idx + tx_num
@@ -716,14 +741,3 @@ class BlockProcessor(server.db.DB):
         self.db_tx_count = self.tx_count
         self.db_height = self.height
         self.db_tip = self.tip
-
-    def get_tx_hash(self, tx_num):
-        '''Returns the tx_hash and height of a tx number.'''
-        tx_hash, tx_height = self.fs_tx_hash(tx_num)
-
-        # Is this unflushed?
-        if tx_hash is None:
-            tx_hashes = self.tx_hashes[tx_height - (self.fs_height + 1)]
-            tx_hash = tx_hashes[tx_num - self.tx_counts[tx_height - 1]]
-
-        return tx_hash, tx_height
diff --git a/server/db.py b/server/db.py
index f6672bc..5dad58b 100644
--- a/server/db.py
+++ b/server/db.py
@@ -50,16 +50,8 @@ class DB(LoggedClass):
         self.logger.info('reorg limit is {:,d} blocks'
                          .format(self.env.reorg_limit))
 
-        # Open DB and metadata files.  Record some of its state.
-        db_name = '{}-{}'.format(self.coin.NAME, self.coin.NET)
-        self.db = open_db(db_name, env.db_engine)
-        if self.db.is_new:
-            self.logger.info('created new {} database {}'
-                             .format(env.db_engine, db_name))
-        else:
-            self.logger.info('successfully opened {} database {}'
-                             .format(env.db_engine, db_name))
-        self.read_state()
+        self.db = None
+        self.reopen_db(True)
 
         create = self.db_height == -1
         self.headers_file = self.open_file('headers', create)
@@ -77,6 +69,43 @@ class DB(LoggedClass):
             assert self.db_tx_count == 0
         self.clean_db()
 
+    def reopen_db(self, first_sync):
+        '''Open the database.  If the database is already open, it is
+        closed (implicitly via GC) and re-opened.
+
+        Re-open to set the maximum number of open files appropriately.
+        '''
+        if self.db:
+            self.logger.info('closing DB to re-open')
+            self.db.close()
+
+        max_open_files = 1024 if first_sync else 256
+
+        # Open DB and metadata files.  Record some of its state.
+        db_name = '{}-{}'.format(self.coin.NAME, self.coin.NET)
+        self.db = open_db(db_name, self.env.db_engine, max_open_files)
+        if self.db.is_new:
+            self.logger.info('created new {} database {}'
+                             .format(self.env.db_engine, db_name))
+        else:
+            self.logger.info('successfully opened {} database {} for sync: {}'
+                             .format(self.env.db_engine, db_name, first_sync))
+        self.read_state()
+
+        if self.first_sync == first_sync:
+            self.logger.info('software version: {}'.format(VERSION))
+            self.logger.info('DB version: {:d}'.format(self.db_version))
+            self.logger.info('coin: {}'.format(self.coin.NAME))
+            self.logger.info('network: {}'.format(self.coin.NET))
+            self.logger.info('height: {:,d}'.format(self.db_height))
+            self.logger.info('tip: {}'.format(hash_to_str(self.db_tip)))
+            self.logger.info('tx count: {:,d}'.format(self.db_tx_count))
+            if self.first_sync:
+                self.logger.info('sync time so far: {}'
+                                 .format(formatted_time(self.wall_time)))
+        else:
+            self.reopen_db(self.first_sync)
+
     def read_state(self):
         if self.db.is_new:
             self.db_height = -1
@@ -110,16 +139,6 @@ class DB(LoggedClass):
             self.wall_time = state['wall_time']
             self.first_sync = state['first_sync']
 
-        self.logger.info('software version: {}'.format(VERSION))
-        self.logger.info('DB version: {:d}'.format(self.db_version))
-        self.logger.info('coin: {}'.format(self.coin.NAME))
-        self.logger.info('network: {}'.format(self.coin.NET))
-        self.logger.info('height: {:,d}'.format(self.db_height))
-        self.logger.info('tip: {}'.format(hash_to_str(self.db_tip)))
-        self.logger.info('tx count: {:,d}'.format(self.db_tx_count))
-        if self.first_sync:
-            self.logger.info('sync time so far: {}'
-                             .format(formatted_time(self.wall_time)))
         if self.flush_count < self.utxo_flush_count:
             raise self.DBError('DB corrupt: flush_count < utxo_flush_count')
 
@@ -251,8 +270,6 @@ class DB(LoggedClass):
             cursor += size
             file_pos += size
 
-        os.sync()
-
     def read_headers(self, start, count):
         '''Requires count >= 0.'''
         # Read some from disk
@@ -332,7 +349,7 @@ class DB(LoggedClass):
             if limit == 0:
                 return
             limit -= 1
-            tx_num, tx_pos = s_unpack('<HI', db_key[-6:])
+            tx_pos, tx_num = s_unpack('<HI', db_key[-6:])
             value, = unpack('<Q', db_value)
             tx_hash, height = self.fs_tx_hash(tx_num)
             yield UTXO(tx_num, tx_pos, tx_hash, height, value)
diff --git a/server/protocol.py b/server/protocol.py
index 7e95a19..bd84a1a 100644
--- a/server/protocol.py
+++ b/server/protocol.py
@@ -254,6 +254,7 @@ class ServerManager(util.LoggedClass):
         def add_future(coro):
             self.futures.append(asyncio.ensure_future(coro))
 
+        # shutdown() assumes bp.main_loop() is first
         add_future(self.bp.main_loop())
         add_future(self.bp.prefetcher.main_loop())
         add_future(self.mempool.main_loop(self.bp.event))
@@ -316,7 +317,9 @@ class ServerManager(util.LoggedClass):
 
     async def shutdown(self):
         '''Call to shutdown the servers.  Returns when done.'''
-        for future in self.futures:
+        self.bp.shutdown()
+        # Don't cancel the block processor main loop - let it close itself
+        for future in self.futures[1:]:
             future.cancel()
         for server in self.servers:
             server.close()
@@ -326,7 +329,6 @@ class ServerManager(util.LoggedClass):
             await asyncio.sleep(0)
         if self.sessions:
             await self.close_sessions()
-        await self.bp.shutdown()
 
     async def close_sessions(self, secs=60):
         self.logger.info('cleanly closing client sessions, please wait...')
diff --git a/server/storage.py b/server/storage.py
index b8a0785..12d7d33 100644
--- a/server/storage.py
+++ b/server/storage.py
@@ -16,12 +16,12 @@ from functools import partial
 from lib.util import subclasses, increment_byte_string
 
 
-def open_db(name, db_engine):
+def open_db(name, db_engine, for_sync):
     '''Returns a database handle.'''
     for db_class in subclasses(Storage):
         if db_class.__name__.lower() == db_engine.lower():
             db_class.import_module()
-            return db_class(name)
+            return db_class(name, for_sync)
 
     raise RuntimeError('unrecognised DB engine "{}"'.format(db_engine))
 
@@ -29,9 +29,9 @@ def open_db(name, db_engine):
 class Storage(object):
     '''Abstract base class of the DB backend abstraction.'''
 
-    def __init__(self, name):
+    def __init__(self, name, for_sync):
         self.is_new = not os.path.exists(name)
-        self.open(name, create=self.is_new)
+        self.open(name, create=self.is_new, for_sync=for_sync)
 
     @classmethod
     def import_module(cls):
@@ -42,6 +42,10 @@ class Storage(object):
         '''Open an existing database or create a new one.'''
         raise NotImplementedError
 
+    def close(self):
+        '''Close an existing database.'''
+        raise NotImplementedError
+
     def get(self, key):
         raise NotImplementedError
 
@@ -75,9 +79,11 @@ class LevelDB(Storage):
         import plyvel
         cls.module = plyvel
 
-    def open(self, name, create):
+    def open(self, name, create, for_sync):
+        mof = 1024 if for_sync else 256
         self.db = self.module.DB(name, create_if_missing=create,
-                                 max_open_files=256, compression=None)
+                                 max_open_files=mof, compression=None)
+        self.close = self.db.close
         self.get = self.db.get
         self.put = self.db.put
         self.iterator = self.db.iterator
@@ -92,18 +98,25 @@ class RocksDB(Storage):
         import rocksdb
         cls.module = rocksdb
 
-    def open(self, name, create):
+    def open(self, name, create, for_sync):
+        mof = 1024 if for_sync else 256
         compression = "no"
         compression = getattr(self.module.CompressionType,
                               compression + "_compression")
         options = self.module.Options(create_if_missing=create,
                                       compression=compression,
                                       target_file_size_base=33554432,
-                                      max_open_files=1024)
+                                      max_open_files=mof)
         self.db = self.module.DB(name, options)
         self.get = self.db.get
         self.put = self.db.put
 
+    def close(self):
+        # PyRocksDB doesn't provide a close method; hopefully this is enough
+        self.db = None
+        import gc
+        gc.collect()
+
     class WriteBatch(object):
         def __init__(self, db):
             self.batch = RocksDB.module.WriteBatch()
@@ -157,11 +170,15 @@ class LMDB(Storage):
         import lmdb
         cls.module = lmdb
 
-    def open(self, name, create):
+    def open(self, name, create, for_sync):
+        # I don't see anything equivalent to max_open_files for for_sync
         self.env = LMDB.module.Environment('.', subdir=True, create=create,
                                           max_dbs=32, map_size=5 * 10 ** 10)
         self.db = self.env.open_db(create=create)
 
+    def close(self):
+        self.env.close()
+
     def get(self, key):
         with self.env.begin(db=self.db) as tx:
             return tx.get(key)
diff --git a/server/version.py b/server/version.py
index 1028f97..3236b2a 100644
--- a/server/version.py
+++ b/server/version.py
@@ -1 +1 @@
-VERSION = "ElectrumX 0.7.11"
+VERSION = "ElectrumX 0.7.12"
diff --git a/tests/test_storage.py b/tests/test_storage.py
index b765c27..2c3d429 100644
--- a/tests/test_storage.py
+++ b/tests/test_storage.py
@@ -21,7 +21,7 @@ for c in subclasses(Storage):
 def db(tmpdir, request):
     cwd = os.getcwd()
     os.chdir(str(tmpdir))
-    db = open_db("db", request.param)
+    db = open_db("db", request.param, False)
     os.chdir(cwd)
     yield db
     # Make sure all the locks and handles are closed
@@ -66,4 +66,4 @@ def test_iterator_reverse(db):
     assert list(db.iterator(prefix=b"abc", reverse=True)) == [
             (b"abc" + str.encode(str(i)), str.encode(str(i))) for
             i in reversed(range(5))
-        ]
\ No newline at end of file
+        ]