diff --git a/CHANGES b/CHANGES
index 1666253015..cb23dc4a12 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,10 @@
+4611.	[bug]		The default LMDB mapsize was too low and caused
+			errors after few thousand zones were added using
+			rndc addzone. A new config option "lmdb-mapsize"
+			has been introduced to configure the LMDB
+			mapsize depending on operational needs.
+			[RT #44954]
+
 4609.	[cleanup]	Rearrange makefiles to enable parallel execution
 			(i.e. "make -j"). [RT #45078]
 
diff --git a/bin/named/config.c b/bin/named/config.c
index 7eacf7ecd7..c70ebd934f 100644
--- a/bin/named/config.c
+++ b/bin/named/config.c
@@ -178,6 +178,7 @@ options {\n\
 	zero-no-soa-ttl-cache no;\n\
 	nsec3-test-zone no;\n\
 	allow-new-zones no;\n\
+	lmdb-mapsize 32M;\n\
 	fetches-per-server 0;\n\
 	require-server-cookie no;\n\
 	v6-bias 50;\n\
diff --git a/bin/named/named.conf.docbook b/bin/named/named.conf.docbook
index 03f592dc88..234bc8d20a 100644
--- a/bin/named/named.conf.docbook
+++ b/bin/named/named.conf.docbook
@@ -1,5 +1,5 @@
 <!--
- - Copyright (C) 2004-2017  Internet Systems Consortium, Inc. ("ISC")
+ - Copyright (C) 2004-2017 Internet Systems Consortium, Inc. ("ISC")
  -
  - This Source Code Form is subject to the terms of the Mozilla Public
  - License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -10,7 +10,7 @@
 
 <refentry xmlns:db="http://docbook.org/ns/docbook" version="5.0" xml:id="man.named.conf">
   <info>
-    <date>2016-12-02</date>
+    <date>2017-04-25</date>
   </info>
   <refentryinfo>
     <corpname>ISC</corpname>
@@ -317,6 +317,7 @@ options {
 	listen-on-v6 <optional> port <replaceable>integer</replaceable> </optional> <optional> dscp
 	    <replaceable>integer</replaceable> </optional> {
 	    <replaceable>address_match_element</replaceable>; ... };
+	lmdb-mapsize <replaceable>sizeval</replaceable>;
 	lock-file ( <replaceable>quoted_string</replaceable> | none );
 	managed-keys-directory <replaceable>quoted_string</replaceable>;
 	masterfile-format ( map | raw | text );
@@ -624,6 +625,7 @@ view <replaceable>string</replaceable> <optional> <replaceable>class</replaceabl
 	};
 	key-directory <replaceable>quoted_string</replaceable>;
 	lame-ttl <replaceable>ttlval</replaceable>;
+	lmdb-mapsize <replaceable>sizeval</replaceable>;
 	managed-keys { <replaceable>string</replaceable> <replaceable>string</replaceable>
 	    <replaceable>integer</replaceable> <replaceable>integer</replaceable> <replaceable>integer</replaceable>
 	    <replaceable>quoted_string</replaceable>; ... };
diff --git a/bin/named/server.c b/bin/named/server.c
index 645301482a..a746178155 100644
--- a/bin/named/server.c
+++ b/bin/named/server.c
@@ -6634,7 +6634,9 @@ setup_newzones(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
 	const cfg_obj_t *maps[4];
 	const cfg_obj_t *options = NULL, *voptions = NULL;
 	const cfg_obj_t *nz = NULL;
+	const cfg_obj_t *obj = NULL;
 	int i = 0;
+	isc_uint64_t mapsize = 0ULL;
 
 	REQUIRE (config != NULL);
 
@@ -6652,6 +6654,32 @@ setup_newzones(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
 	if (result == ISC_R_SUCCESS)
 		allow = cfg_obj_asboolean(nz);
 
+#ifdef HAVE_LMDB
+	result = ns_config_get(maps, "lmdb-mapsize", &obj);
+	if (result == ISC_R_SUCCESS && obj != NULL) {
+		mapsize = cfg_obj_asuint64(obj);
+		if (mapsize < (1ULL << 20)) { /* 1 megabyte */
+			cfg_obj_log(obj, ns_g_lctx,
+				    ISC_LOG_ERROR,
+				    "'lmdb-mapsize "
+				    "%" ISC_PRINT_QUADFORMAT "d' "
+				    "is too small",
+				    mapsize);
+			return (ISC_R_FAILURE);
+		} else if (mapsize > (1ULL << 40)) { /* 1 terabyte */
+			cfg_obj_log(obj, ns_g_lctx,
+				    ISC_LOG_ERROR,
+				    "'lmdb-mapsize "
+				    "%" ISC_PRINT_QUADFORMAT "d' "
+				    "is too large",
+				    mapsize);
+			return (ISC_R_FAILURE);
+		}
+	}
+#else
+	UNUSED(obj);
+#endif /* HAVE_LMDB */
+
 	/*
 	 * A non-empty catalog-zones statement implies allow-new-zones
 	 */
@@ -6667,7 +6695,7 @@ setup_newzones(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
 	}
 
 	if (!allow) {
-		dns_view_setnewzones(view, ISC_FALSE, NULL, NULL);
+		dns_view_setnewzones(view, ISC_FALSE, NULL, NULL, 0ULL);
 		if (num_zones != NULL)
 			*num_zones = 0;
 		return (ISC_R_SUCCESS);
@@ -6675,14 +6703,14 @@ setup_newzones(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
 
 	nzcfg = isc_mem_get(view->mctx, sizeof(*nzcfg));
 	if (nzcfg == NULL) {
-		dns_view_setnewzones(view, ISC_FALSE, NULL, NULL);
+		dns_view_setnewzones(view, ISC_FALSE, NULL, NULL, 0ULL);
 		return (ISC_R_NOMEMORY);
 	}
 
 	memset(nzcfg, 0, sizeof(*nzcfg));
 
 	result = dns_view_setnewzones(view, allow, nzcfg,
-				      newzone_cfgctx_destroy);
+				      newzone_cfgctx_destroy, mapsize);
 	if (result != ISC_R_SUCCESS) {
 		isc_mem_free(view->mctx, nzcfg);
 		return (result);
@@ -11032,11 +11060,25 @@ nzd_save(MDB_txn **txnp, MDB_dbi dbi, dns_zone_t *zone,
 		const cfg_obj_t *zoptions;
 
 		result = isc_buffer_allocate(view->mctx, &text, 256);
-		if (result != ISC_R_SUCCESS)
+		if (result != ISC_R_SUCCESS) {
+			isc_log_write(ns_g_lctx,
+				      NS_LOGCATEGORY_GENERAL,
+				      NS_LOGMODULE_SERVER,
+				      ISC_LOG_ERROR,
+				      "Unable to allocate buffer in "
+				      "nzd_save(): %s",
+				      isc_result_totext(result));
 			goto cleanup;
+		}
 
 		zoptions = cfg_tuple_get(zconfig, "options");
 		if (zoptions == NULL) {
+			isc_log_write(ns_g_lctx,
+				      NS_LOGCATEGORY_GENERAL,
+				      NS_LOGMODULE_SERVER,
+				      ISC_LOG_ERROR,
+				      "Unable to get options from config in "
+				      "nzd_save()");
 			result = ISC_R_FAILURE;
 			goto cleanup;
 		}
@@ -11069,8 +11111,16 @@ nzd_save(MDB_txn **txnp, MDB_dbi dbi, dns_zone_t *zone,
 		(void) mdb_txn_abort(*txnp);
 	else {
 		status = mdb_txn_commit(*txnp);
-		if (status != 0)
+		if (status != 0) {
+			isc_log_write(ns_g_lctx,
+				      NS_LOGCATEGORY_GENERAL,
+				      NS_LOGMODULE_SERVER,
+				      ISC_LOG_ERROR,
+				      "Error committing "
+				      "NZD database: %s",
+				      mdb_strerror(status));
 			result = ISC_R_FAILURE;
+		}
 	}
 	*txnp = NULL;
 
@@ -11573,7 +11623,16 @@ do_addzone(ns_server_t *server, ns_cfgctx_t *cfg, dns_view_t *view,
 	}
 
 	/* Is it there yet? */
-	CHECK(dns_zt_find(view->zonetable, name, 0, NULL, &zone));
+	result = dns_zt_find(view->zonetable, name, 0, NULL, &zone);
+	if (result != ISC_R_SUCCESS) {
+		isc_log_write(ns_g_lctx,
+			      NS_LOGCATEGORY_GENERAL,
+			      NS_LOGMODULE_SERVER,
+			      ISC_LOG_ERROR,
+			      "added new zone was not found: %s",
+			      isc_result_totext(result));
+		goto cleanup;
+	}
 
 #ifndef HAVE_LMDB
 	/*
diff --git a/bin/tests/system/checkconf/bad-lmdb-mapsize-bogus.conf b/bin/tests/system/checkconf/bad-lmdb-mapsize-bogus.conf
new file mode 100644
index 0000000000..f27e87f217
--- /dev/null
+++ b/bin/tests/system/checkconf/bad-lmdb-mapsize-bogus.conf
@@ -0,0 +1,11 @@
+/*
+ * Copyright (C) 2016  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+options {
+	lmdb-mapsize bogusvalue;
+};
diff --git a/bin/tests/system/checkconf/bad-lmdb-mapsize-toolarge.conf b/bin/tests/system/checkconf/bad-lmdb-mapsize-toolarge.conf
new file mode 100644
index 0000000000..3315091a8f
--- /dev/null
+++ b/bin/tests/system/checkconf/bad-lmdb-mapsize-toolarge.conf
@@ -0,0 +1,11 @@
+/*
+ * Copyright (C) 2016  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+options {
+	lmdb-mapsize 2048G;
+};
diff --git a/bin/tests/system/checkconf/bad-lmdb-mapsize-toosmall.conf b/bin/tests/system/checkconf/bad-lmdb-mapsize-toosmall.conf
new file mode 100644
index 0000000000..803ea6b3e5
--- /dev/null
+++ b/bin/tests/system/checkconf/bad-lmdb-mapsize-toosmall.conf
@@ -0,0 +1,11 @@
+/*
+ * Copyright (C) 2016  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+options {
+	lmdb-mapsize 1;
+};
diff --git a/bin/tests/system/checkconf/bad-lmdb-mapsize-unlimited.conf b/bin/tests/system/checkconf/bad-lmdb-mapsize-unlimited.conf
new file mode 100644
index 0000000000..b1b8066a00
--- /dev/null
+++ b/bin/tests/system/checkconf/bad-lmdb-mapsize-unlimited.conf
@@ -0,0 +1,11 @@
+/*
+ * Copyright (C) 2016  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+options {
+	lmdb-mapsize unlimited;
+};
diff --git a/bin/tests/system/checkconf/good-lmdb-mapsize-largest.conf b/bin/tests/system/checkconf/good-lmdb-mapsize-largest.conf
new file mode 100644
index 0000000000..9625e579d7
--- /dev/null
+++ b/bin/tests/system/checkconf/good-lmdb-mapsize-largest.conf
@@ -0,0 +1,11 @@
+/*
+ * Copyright (C) 2016  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+options {
+	lmdb-mapsize 1024G;
+};
diff --git a/bin/tests/system/checkconf/good-lmdb-mapsize-smallest.conf b/bin/tests/system/checkconf/good-lmdb-mapsize-smallest.conf
new file mode 100644
index 0000000000..0f6fa79352
--- /dev/null
+++ b/bin/tests/system/checkconf/good-lmdb-mapsize-smallest.conf
@@ -0,0 +1,11 @@
+/*
+ * Copyright (C) 2016  Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+options {
+	lmdb-mapsize 1M;
+};
diff --git a/doc/arm/Bv9ARM-book.xml b/doc/arm/Bv9ARM-book.xml
index a2aebc9a88..def6483cb3 100644
--- a/doc/arm/Bv9ARM-book.xml
+++ b/doc/arm/Bv9ARM-book.xml
@@ -5045,6 +5045,31 @@ badresp:1,adberr:0,findfail:0,valfail:0]
 	    </listitem>
 	  </varlistentry>
 
+	  <varlistentry>
+	    <term><command>lmdb-mapsize</command></term>
+	    <listitem>
+	      <para>
+		When <command>named</command> is built with liblmdb,
+		this option sets a maximum size for the memory map of
+		the new-zone database (NZD) in LMDB database format.
+		This database is used to store configuration information
+		for zones added using <command>rndc addzone</command>.
+		Note that this is not the NZD database file size, but
+		the largest size that the database may grow to.
+	      </para>
+	      <para>
+		Because the database file is memory mapped, its size is
+		limited by the address space of the named process.  The
+		default of 32 megabytes was chosen to be usable with
+		32-bit <command>named</command> builds.  The largest
+		permitted value is 1 terabyte. Given typical zone
+		configurations without elaborate ACLs, a 32 MB NZD file
+		ought to be able to hold configurations of about 100,000
+		zones.
+	      </para>
+	    </listitem>
+	  </varlistentry>
+
 	  <varlistentry>
 	    <term><command>managed-keys-directory</command></term>
 	    <listitem>
@@ -5889,6 +5914,29 @@ options {
 		  added at runtime via <command>rndc addzone</command>.
 		  The default is <userinput>no</userinput>.
 		</para>
+		<para>
+		  Newly added zones' configuration parameters
+		  are stored so that they can persist after the
+		  server is restarted.  The configuration information
+		  is saved in a file called
+		  <filename><replaceable>viewname</replaceable>.nzf</filename>
+		  (or, if <command>named</command> is compiled with
+		  liblmdb, in an LMDB database file called
+		  <filename><replaceable>viewname</replaceable>.nzd</filename>).
+		  <replaceable>viewname</replaceable> is the name of the
+		  view, unless the view name contains characters that are
+		  incompatible with use as a file name, in which case a
+		  cryptographic hash of the view name is used instead.
+		</para>
+		<para>
+		  Zones added at runtime will have their configuration
+		  stored either in a new-zone file (NZF) or a new-zone
+		  database (NZD) depending on whether
+		  <command>named</command> was linked with
+		  liblmdb at compile time.
+		  See <xref linkend="man.rndc"/> for further details
+		  about <command>rndc addzone</command>.
+		</para>
 	      </listitem>
 	    </varlistentry>
 
diff --git a/doc/misc/options b/doc/misc/options
index 37683a7977..4239bec2e6 100644
--- a/doc/misc/options
+++ b/doc/misc/options
@@ -204,6 +204,7 @@ options {
         listen-on-v6 [ port <integer> ] [ dscp
             <integer> ] {
             <address_match_element>; ... }; // may occur multiple times
+        lmdb-mapsize <sizeval>;
         lock-file ( <quoted_string> | none );
         maintain-ixfr-base <boolean>; // obsolete
         managed-keys-directory <quoted_string>;
@@ -514,6 +515,7 @@ view <string> [ <class> ] {
         }; // may occur multiple times
         key-directory <quoted_string>;
         lame-ttl <ttlval>;
+        lmdb-mapsize <sizeval>;
         maintain-ixfr-base <boolean>; // obsolete
         managed-keys { <string> <string>
             <integer> <integer> <integer>
diff --git a/lib/bind9/check.c b/lib/bind9/check.c
index c13b947eed..abd459005b 100644
--- a/lib/bind9/check.c
+++ b/lib/bind9/check.c
@@ -22,6 +22,7 @@
 #include <isc/netaddr.h>
 #include <isc/parseint.h>
 #include <isc/platform.h>
+#include <isc/print.h>
 #include <isc/region.h>
 #include <isc/result.h>
 #include <isc/sha1.h>
@@ -1439,6 +1440,30 @@ check_options(const cfg_obj_t *options, isc_log_t *logctx, isc_mem_t *mctx,
 	}
 #endif
 
+	obj = NULL;
+	(void)cfg_map_get(options, "lmdb-mapsize", &obj);
+	if (obj != NULL) {
+		isc_uint64_t mapsize = cfg_obj_asuint64(obj);
+
+		if (mapsize < (1ULL << 20)) { /* 1 megabyte */
+			cfg_obj_log(obj, logctx,
+				    ISC_LOG_ERROR,
+				    "'lmdb-mapsize "
+				    "%" ISC_PRINT_QUADFORMAT "d' "
+				    "is too small",
+				    mapsize);
+			return (ISC_R_RANGE);
+		} else if (mapsize > (1ULL << 40)) { /* 1 terabyte */
+			cfg_obj_log(obj, logctx,
+				    ISC_LOG_ERROR,
+				    "'lmdb-mapsize "
+				    "%" ISC_PRINT_QUADFORMAT "d' "
+				    "is too large",
+				    mapsize);
+			return (ISC_R_RANGE);
+		}
+	}
+
 	return (result);
 }
 
diff --git a/lib/dns/include/dns/view.h b/lib/dns/include/dns/view.h
index ebfb127921..0e73ad4750 100644
--- a/lib/dns/include/dns/view.h
+++ b/lib/dns/include/dns/view.h
@@ -1212,7 +1212,7 @@ dns_view_untrust(dns_view_t *view, dns_name_t *keyname,
 
 isc_result_t
 dns_view_setnewzones(dns_view_t *view, isc_boolean_t allow, void *cfgctx,
-		     void (*cfg_destroy)(void **));
+		     void (*cfg_destroy)(void **), isc_uint64_t mapsize);
 /*%<
  * Set whether or not to allow zones to be created or deleted at runtime.
  *
diff --git a/lib/dns/view.c b/lib/dns/view.c
index 288ef6ce60..f2c10717bc 100644
--- a/lib/dns/view.c
+++ b/lib/dns/view.c
@@ -507,7 +507,7 @@ destroy(dns_view_t *view) {
 	if (view->dtenv != NULL)
 		dns_dt_detach(&view->dtenv);
 #endif /* HAVE_DNSTAP */
-	dns_view_setnewzones(view, ISC_FALSE, NULL, NULL);
+	dns_view_setnewzones(view, ISC_FALSE, NULL, NULL, 0ULL);
 	if (view->new_zone_file != NULL) {
 		isc_mem_free(view->mctx, view->new_zone_file);
 		view->new_zone_file = NULL;
@@ -1986,7 +1986,7 @@ dns_view_untrust(dns_view_t *view, dns_name_t *keyname,
 
 isc_result_t
 dns_view_setnewzones(dns_view_t *view, isc_boolean_t allow, void *cfgctx,
-		     void (*cfg_destroy)(void **))
+		     void (*cfg_destroy)(void **), isc_uint64_t mapsize)
 {
 	isc_result_t result;
 	char buffer[1024];
@@ -2042,6 +2042,14 @@ dns_view_setnewzones(dns_view_t *view, isc_boolean_t allow, void *cfgctx,
 		goto out;
 	}
 
+	if (mapsize != 0ULL) {
+		status = mdb_env_set_mapsize(env, mapsize);
+		if (status != 0) {
+			result = ISC_R_FAILURE;
+			goto out;
+		}
+	}
+
 	status = mdb_env_open(env, view->new_zone_db,
 			      MDB_NOSUBDIR|MDB_CREATE, 0600);
 	if (status != 0) {
diff --git a/lib/isccfg/include/isccfg/grammar.h b/lib/isccfg/include/isccfg/grammar.h
index 087db23a10..e5fb79f1ae 100644
--- a/lib/isccfg/include/isccfg/grammar.h
+++ b/lib/isccfg/include/isccfg/grammar.h
@@ -48,6 +48,9 @@
 #define CFG_CLAUSEFLAG_NOTCONFIGURED	0x00000080
 /*% A option for a experimental feature. */
 #define CFG_CLAUSEFLAG_EXPERIMENTAL	0x00000100
+/*% A configuration option that is ineffective due to
+ * compile time options, but is harmless. */
+#define CFG_CLAUSEFLAG_NOOP		0x00000200
 
 typedef struct cfg_clausedef cfg_clausedef_t;
 typedef struct cfg_tuplefielddef cfg_tuplefielddef_t;
diff --git a/lib/isccfg/namedconf.c b/lib/isccfg/namedconf.c
index 1488e83203..e34009a7b4 100644
--- a/lib/isccfg/namedconf.c
+++ b/lib/isccfg/namedconf.c
@@ -131,6 +131,7 @@ static cfg_type_t cfg_type_server_key_kludge;
 static cfg_type_t cfg_type_size;
 static cfg_type_t cfg_type_sizenodefault;
 static cfg_type_t cfg_type_sizeorpercent;
+static cfg_type_t cfg_type_sizeval;
 static cfg_type_t cfg_type_sockaddr4wild;
 static cfg_type_t cfg_type_sockaddr6wild;
 static cfg_type_t cfg_type_statschannels;
@@ -1755,6 +1756,11 @@ view_clauses[] = {
 #endif
 	{ "ixfr-from-differences", &cfg_type_ixfrdifftype, 0 },
 	{ "lame-ttl", &cfg_type_ttlval, 0 },
+#ifdef HAVE_LMDB
+	{ "lmdb-mapsize", &cfg_type_sizeval, 0 },
+#else
+	{ "lmdb-mapsize", &cfg_type_sizeval, CFG_CLAUSEFLAG_NOOP },
+#endif
 	{ "nocookie-udp-size", &cfg_type_uint32, 0 },
 	{ "nosit-udp-size", &cfg_type_uint32, CFG_CLAUSEFLAG_OBSOLETE },
 	{ "max-acache-size", &cfg_type_sizenodefault, 0 },
diff --git a/lib/isccfg/parser.c b/lib/isccfg/parser.c
index c77cbefbce..13c5151ad4 100644
--- a/lib/isccfg/parser.c
+++ b/lib/isccfg/parser.c
@@ -1717,6 +1717,12 @@ cfg_parse_mapbody(cfg_parser_t *pctx, const cfg_type_t *type, cfg_obj_t **ret)
 			cfg_parser_warning(pctx, 0, "option '%s' is "
 				       "not implemented", clause->name);
 
+		if ((clause->flags & CFG_CLAUSEFLAG_NOOP) != 0) {
+			cfg_parser_warning(pctx, 0, "option '%s' was not "
+					   "enabled at compile time "
+					   "(ignored)", clause->name);
+		}
+
 		if ((clause->flags & CFG_CLAUSEFLAG_NOTCONFIGURED) != 0) {
 			cfg_parser_warning(pctx, 0, "option '%s' was not "
 					   "enabled at compile time",
@@ -1973,6 +1979,7 @@ static struct flagtext {
 	{ CFG_CLAUSEFLAG_NOTCONFIGURED, "not configured" },
 	{ CFG_CLAUSEFLAG_MULTI, "may occur multiple times" },
 	{ CFG_CLAUSEFLAG_EXPERIMENTAL, "experimental" },
+	{ CFG_CLAUSEFLAG_NOOP, "non-operational" },
 	{ 0, NULL }
 };