diff --git a/sr_port/anticipatory_freeze.h b/sr_port/anticipatory_freeze.h
index 6b297b0c7..f929a0a9a 100644
--- a/sr_port/anticipatory_freeze.h
+++ b/sr_port/anticipatory_freeze.h
@@ -3,7 +3,7 @@
  * Copyright (c) 2012-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2018-2020 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2018-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -335,6 +335,10 @@ MBSTART {															\
 #define DB_LSEEKWRITE_HANG(CSA)	FALSE
 #endif
 
+#ifdef DEBUG
+GBLREF	gtm_int8	ydb_skip_bml_num;	/* Use "gtm_int8" since it is possible "block_id" type is not yet defined */
+#endif
+
 /* #GTM_THREAD_SAFE : The below macro (DB_LSEEKWRITE) is thread-safe */
 #define	DB_LSEEKWRITE(CSA, UDI, DB_FN, FD, OFFSET, BUFF, SIZE, STATUS)							\
 MBSTART {														\
@@ -344,6 +348,11 @@ MBSTART {														\
 	assert(!CSA_LOCAL || !CSA_LOCAL->region || FILE_INFO(CSA_LOCAL->region)->grabbed_access_sem			\
 			|| !(CSA_LOCAL)->nl || !FROZEN_CHILLED(CSA_LOCAL) || FREEZE_LATCH_HELD(CSA_LOCAL));		\
 	DBG_CHECK_DIO_ALIGNMENT(UDI, OFFSET, BUFF, SIZE);								\
+	assert((0 == ydb_skip_bml_num) || (NULL == UDI) || (0 == OFFSET)						\
+		|| ((BLK_ZERO_OFF(((unix_db_info *)UDI)->s_addrs.hdr->start_vbn)					\
+			+ ((gtm_int8)BLKS_PER_LMAP * ((unix_db_info *)UDI)->s_addrs.hdr->blk_size)) > OFFSET)		\
+		|| ((BLK_ZERO_OFF(((unix_db_info *)UDI)->s_addrs.hdr->start_vbn)					\
+			+ (ydb_skip_bml_num * ((unix_db_info *)UDI)->s_addrs.hdr->blk_size)) <= OFFSET));		\
 	/* We should never write to a READ_ONLY db file header unless we hold standalone access on the db */		\
 	assert((0 != OFFSET) || !((sgmnt_data_ptr_t)BUFF)->read_only || (NULL == UDI) || UDI->grabbed_access_sem);	\
 	DO_LSEEKWRITE(CSA_LOCAL, DB_FN, FD, OFFSET, BUFF, SIZE, STATUS, fake_db_enospc, DB_LSEEKWRITE_HANG(CSA),	\
diff --git a/sr_port/bm_getfree.c b/sr_port/bm_getfree.c
index 84300d41c..4268f48c5 100644
--- a/sr_port/bm_getfree.c
+++ b/sr_port/bm_getfree.c
@@ -70,6 +70,10 @@ GBLREF uint4		dollar_tlevel;
 GBLREF uint4		update_array_size, cumul_update_array_size;
 GBLREF unsigned int	t_tries;
 
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
 error_def(ERR_DBBADFREEBLKCTR);
 error_def(ERR_DBMBMINCFREFIXED);
 
@@ -89,6 +93,10 @@ block_id bm_getfree(block_id hint, boolean_t *blk_used, unsigned int cw_work, cw
 	total_blks = (dba_mm == cs_data->acc_meth) ? cs_addrs->total_blks : cs_addrs->ti->total_blks;
 	if (hint >= total_blks)		/* for TP, hint can be > total_blks */
 		hint = 1;
+#	ifdef DEBUG
+	if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= hint) && (hint < ydb_skip_bml_num))
+		hint = ydb_skip_bml_num;
+#	endif
 	hint_cycled = DIVIDE_ROUND_UP(total_blks, BLKS_PER_LMAP);
 	hint_limit = DIVIDE_ROUND_DOWN(hint, BLKS_PER_LMAP);
 	local_maps = hint_cycled + 2;	/* for (up to) 2 wraps */
@@ -102,6 +110,10 @@ block_id bm_getfree(block_id hint, boolean_t *blk_used, unsigned int cw_work, cw
 			{
 				hint_cycled = hint_limit;
 				hint = 1;
+#				ifdef DEBUG
+				if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= hint) && (hint < ydb_skip_bml_num))
+					hint = ydb_skip_bml_num;
+#				endif
 				continue;
 			}
 			if (SS_NORMAL != (status = GDSFILEXT(cs_data->extension_size, total_blks, TRANS_IN_PROG_TRUE)))
@@ -125,6 +137,13 @@ block_id bm_getfree(block_id hint, boolean_t *blk_used, unsigned int cw_work, cw
 			continue;
 		}
 		bml *= BLKS_PER_LMAP;
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= bml) && (bml < ydb_skip_bml_num))
+		{
+			hint = ydb_skip_bml_num + 1;
+			continue;
+		}
+#		endif
 		if (ROUND_DOWN2(hint, BLKS_PER_LMAP) != bml)
 		{	/* not within requested map */
 			if ((bml < hint) && (hint_cycled))	/* wrap? - second one should force an extend for sure */
@@ -271,6 +290,17 @@ boolean_t	is_free_blks_ctr_ok(void)
 	local_maps = DIVIDE_ROUND_UP(total_blks, BLKS_PER_LMAP);
 	for (free_blocks = 0, free_bml = 0; free_bml < local_maps; free_bml++)
 	{
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num)
+			&& (BLKS_PER_LMAP <= (BLKS_PER_LMAP * free_bml))
+			&& ((BLKS_PER_LMAP * free_bml) < ydb_skip_bml_num))
+		{
+			free_bml = (ydb_skip_bml_num / BLKS_PER_LMAP) - 1;
+				/* - 1 to compensate the "free_bml++" done in "for" loop line */
+			free_blocks += (ydb_skip_bml_num - BLKS_PER_LMAP) / BLKS_PER_LMAP * (BLKS_PER_LMAP - 1);
+			continue;
+		}
+#		endif
 		bml = bmm_find_free((uint4)free_bml, (sm_uc_ptr_t)MM_ADDR(cs_data), local_maps);
 		if (bml < free_bml)
 			break;
@@ -299,6 +329,7 @@ boolean_t	is_free_blks_ctr_ok(void)
 	assert(cs_addrs->ti->free_blocks == free_blocks);
 	if (cs_addrs->ti->free_blocks != free_blocks)
 	{
+		assert(FALSE);
 		send_msg_csa(CSA_ARG(cs_addrs) VARLSTCNT(6) ERR_DBBADFREEBLKCTR, 4, DB_LEN_STR(gv_cur_region),
 				&(cs_addrs->ti->free_blocks), &free_blocks);
 		cs_addrs->ti->free_blocks = free_blocks;
diff --git a/sr_port/dse_maps.c b/sr_port/dse_maps.c
index 91bb55806..5234afa21 100644
--- a/sr_port/dse_maps.c
+++ b/sr_port/dse_maps.c
@@ -3,6 +3,9 @@
  * Copyright (c) 2001-2021 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
+ * Copyright (c) 2023 YottaDB LLC and/or its subsidiaries.	*
+ * All rights reserved.						*
+ *								*
  *	This source code contains the intellectual property	*
  *	of its copyright holder(s), and is made available	*
  *	under a license.  If you do not know the terms of	*
@@ -56,6 +59,10 @@ GBLREF short		crash_count;
 GBLREF srch_hist	dummy_hist;
 GBLREF uint4		update_array_size;
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 error_def(ERR_DBRDONLY);
 error_def(ERR_DSEBLKRDFAIL);
 error_def(ERR_DSEFAIL);
@@ -120,6 +127,13 @@ void dse_maps(void)
 		dse_m_rest(blk, bml_list, bml_size, &csa->ti->free_blocks, TRUE);
 		for (blk_index = 0, bml_index = 0;  blk_index < total_blks; blk_index += bplmap, bml_index++)
 		{
+#			ifdef DEBUG
+			if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP == blk_index))
+			{
+				bml_index += (ydb_skip_bml_num - blk_index) / BLKS_PER_LMAP;
+				blk_index = ydb_skip_bml_num;
+			}
+#			endif
 			t_begin_crit(ERR_DSEFAIL);
 			CHECK_TN(csa, csd, csd->trans_hist.curr_tn);	/* can issue rts_error TNTOOLARGE */
 			CWS_RESET;
diff --git a/sr_port/dse_range.c b/sr_port/dse_range.c
index 32d88f5c2..75abfd771 100644
--- a/sr_port/dse_range.c
+++ b/sr_port/dse_range.c
@@ -41,6 +41,10 @@ GBLREF short int	patch_path_count;
 GBLREF sgmnt_addrs	*cs_addrs;
 GBLREF VSIG_ATOMIC_T	util_interrupt;
 
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
 error_def(ERR_CTRLC);
 error_def(ERR_DSEBLKRDFAIL);
 error_def(ERR_DSEINVALBLKID);
@@ -103,6 +107,13 @@ void dse_range(void)
 	DSE_GRAB_CRIT_AS_APPROPRIATE(was_crit, was_hold_onto_crit, nocrit_present, cs_addrs, gv_cur_region);
 	for (blk = from; blk <= to ;blk++)
 	{
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= blk) && (blk < ydb_skip_bml_num))
+		{
+			blk = ydb_skip_bml_num - 1;
+			continue;
+		}
+#		endif
 		if (util_interrupt)
 		{
 			DSE_REL_CRIT_AS_APPROPRIATE(was_crit, was_hold_onto_crit, nocrit_present, cs_addrs, gv_cur_region);
diff --git a/sr_port/gbldefs.c b/sr_port/gbldefs.c
index 8d158c6ad..3559912ae 100644
--- a/sr_port/gbldefs.c
+++ b/sr_port/gbldefs.c
@@ -1419,3 +1419,6 @@ GBLDEF	boolean_t	ydb_treat_sigusr2_like_sigusr1;	/* set based on env var "ydb_tr
 GBLDEF	int		jobinterrupt_sig_num;		/* Set to signal number that caused $ZINTERRUPT (SIGUSR1/SIGUSR2).
 							 * Used to derive the value of the ISV $ZYINTRSIG.
 							 */
+#ifdef DEBUG
+GBLDEF	block_id	ydb_skip_bml_num;	/* See comment in "sr_port/gtm_env_init.c" for purpose */
+#endif
diff --git a/sr_port/gtm_env_init.c b/sr_port/gtm_env_init.c
index bbb4d8ab4..fc61e67c3 100644
--- a/sr_port/gtm_env_init.c
+++ b/sr_port/gtm_env_init.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2004-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2017-2022 YottaDB LLC and/or its subsidiaries. *
+ * Copyright (c) 2017-2023 YottaDB LLC and/or its subsidiaries. *
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -87,6 +87,10 @@ GBLREF	int		ydb_repl_filter_timeout;/* # of seconds that source server waits bef
 GBLREF  boolean_t 	dollar_test_default; 	/* Default value taken by dollar_truth via dollar_test_default */
 GBLREF	boolean_t	gtm_nofflf;		/* Used to control "write #" behavior ref GTM-9136 */
 
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
 void	gtm_env_init(void)
 {
 	boolean_t		ret, is_defined;
@@ -223,6 +227,18 @@ void	gtm_env_init(void)
 		ret = ydb_logical_truth_value(YDBENVINDX_DIRTREE_COLLHDR_ALWAYS, FALSE, &is_defined);
 		if (is_defined)
 			TREF(ydb_dirtree_collhdr_always) = ret; /* if logical is not defined, the TREF takes the default value */
+		/* ydb_test_4g_db_blks env var. If set to a non-zero value of N, it implies blocks from the 1st local bitmap
+		 * to the N-1th local bitmap block are not allocated in the db file. After the 0th local bitmap block, the
+		 * Nth local bitmap block is where block allocation continues. This helps test records in the database blocks
+		 * that contain 8-byte block numbers where the higher order 4-byte is non-zero. This effectively tests all
+		 * code (mostly added in GT.M V7.0-000 and merged into YottaDB r2.00) that handles 8-byte block numbers.
+		 * A 0 value implies this scheme is disabled.
+		 */
+		ydb_skip_bml_num = (block_id)ydb_trans_numeric(YDBENVINDX_TEST_4G_DB_BLKS, &is_defined, IGNORE_ERRORS_TRUE, NULL);
+		if (!is_defined)
+			ydb_skip_bml_num = 0;
+		else
+			ydb_skip_bml_num *= BLKS_PER_LMAP;
 #		endif
 		/* GDS Block certification */
 		ret = ydb_logical_truth_value(YDBENVINDX_GDSCERT, FALSE, &is_defined);
diff --git a/sr_port/mu_int_blk.c b/sr_port/mu_int_blk.c
index b321b291d..65287b54c 100644
--- a/sr_port/mu_int_blk.c
+++ b/sr_port/mu_int_blk.c
@@ -147,7 +147,7 @@ GBLREF gtm_uint64_t		mu_int_cum[CUM_TYPE_MAX][MAX_BT_DEPTH + 1];
 GBLREF uint4			mu_int_offset[];
 GBLREF uint4			mu_int_errknt;
 GBLREF block_id			mu_int_path[];
-GBLREF int4			mu_int_blks_to_upgrd;
+GBLREF block_id			mu_int_blks_to_upgrd;
 GBLREF global_list		*trees;
 GBLREF global_list		*trees_tail;
 GBLREF gv_key			*mu_end_key;
diff --git a/sr_port/mu_int_init.c b/sr_port/mu_int_init.c
index 3d7d041aa..188bfc241 100644
--- a/sr_port/mu_int_init.c
+++ b/sr_port/mu_int_init.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2018 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2019-2022 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2019-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -91,6 +91,11 @@ boolean_t mu_int_init(void)
 	fc->op = FC_READ;
 	/* Do aligned reads if opened with O_DIRECT */
 	udi = FC2UDI(fc);
+#	ifdef DEBUG
+	udi->s_addrs.hdr = NULL;	/* Clear previous value of udi->s_addrs.hdr as it would have been freed up
+					 * inside STANDALONE macro invoked above.
+					 */
+#	endif
 	tsd = udi->fd_opened_with_o_direct ? (sgmnt_data_ptr_t)(TREF(dio_buff)).aligned : &mu_int_data;
 	fc->op_buff = (uchar_ptr_t)tsd;
 	fc->op_len = SGMNT_HDR_LEN;
@@ -99,6 +104,11 @@ boolean_t mu_int_init(void)
 	/* Ensure "mu_int_data" is populated even if we did not directly read into it for the O_DIRECT case */
 	if (udi->fd_opened_with_o_direct)
 		memcpy(&mu_int_data, (TREF(dio_buff)).aligned, SGMNT_HDR_LEN);
+#	ifdef DEBUG
+	udi->s_addrs.hdr = &mu_int_data;	/* Now that we have read in the file header, point udi to it for the next dbfilop.
+						 * This is used by the DB_LSEEKREAD macro if "ydb_skip_bml_num" is non-zero.
+						 */
+#	endif
 	if (MASTER_MAP_SIZE_MAX < MASTER_MAP_SIZE(&mu_int_data) ||
 	    native_size < DIVIDE_ROUND_UP(SGMNT_HDR_LEN + MASTER_MAP_SIZE(&mu_int_data), DISK_BLOCK_SIZE) + MIN_DB_BLOCKS)
 	{
diff --git a/sr_port/mu_int_maps.c b/sr_port/mu_int_maps.c
index 15dc1412a..adf524263 100644
--- a/sr_port/mu_int_maps.c
+++ b/sr_port/mu_int_maps.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2022 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2022-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -43,7 +43,7 @@ GBLREF	sgmnt_data		mu_int_data;
 GBLREF	block_id		mu_int_path[];
 GBLREF	boolean_t		tn_reset_this_reg;
 GBLREF	int			mu_int_plen;
-GBLREF	int4			mu_int_blks_to_upgrd;
+GBLREF	block_id		mu_int_blks_to_upgrd;
 GBLREF	int			disp_map_errors;
 GBLREF	int			mu_map_errs;
 GBLREF	int			disp_trans_errors;
@@ -54,6 +54,10 @@ GBLREF	sgmnt_addrs		*cs_addrs;
 
 GBLREF trans_num	largest_tn;
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 error_def(ERR_DBREADBM);
 error_def(ERR_DBLVLINC);
 error_def(ERR_DBMBSIZMN);
@@ -119,6 +123,10 @@ void mu_int_maps(void)
 	{
 		assert(mapsize == mu_int_data.bplmap);
 		blkno = mcnt * mu_int_data.bplmap;
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (0 < blkno) && (blkno < ydb_skip_bml_num))
+			continue;
+#		endif
 		bml_busy(0, mu_int_locals + ((blkno * BML_BITS_PER_BLK) / BITS_PER_UCHAR));
 		blk_base = mu_int_read(blkno, &ondsk_blkver, &free_blk_base);	/* ondsk_blkver set to GDSV4 or GDSV6 (GDSVCURR) */
 		if (!blk_base)
diff --git a/sr_port/mu_reorg_upgrd_dwngrd.c b/sr_port/mu_reorg_upgrd_dwngrd.c
index 36bae5663..ee8f57e23 100644
--- a/sr_port/mu_reorg_upgrd_dwngrd.c
+++ b/sr_port/mu_reorg_upgrd_dwngrd.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2005-2021 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2018-2020 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2018-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -89,6 +89,10 @@ GBLREF	unsigned char		cw_set_depth;
 GBLREF	unsigned char		cw_map_depth;
 GBLREF	uint4			update_trans;
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 error_def(ERR_BUFFLUFAILED);
 error_def(ERR_DBBTUWRNG);
 error_def(ERR_DBFILERR);
@@ -328,6 +332,13 @@ void	mu_reorg_upgrd_dwngrd(void)
 		memset(&reorg_stats, 0, SIZEOF(reorg_stats));	/* initialize statistics for this region */
 		for (curbmp = start_bmp; curbmp <= last_bmp; curbmp += BLKS_PER_LMAP)
 		{
+#			ifdef DEBUG
+			if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= curbmp) && (curbmp < ydb_skip_bml_num))
+			{
+				curbmp = ydb_skip_bml_num - BLKS_PER_LMAP;
+				continue;
+			}
+#			endif
 			if (mu_ctrly_occurred || mu_ctrlc_occurred)
 			{
 				status1 = ERR_MUNOFINISH;
diff --git a/sr_port/mu_swap_blk.c b/sr_port/mu_swap_blk.c
index fd9c718f6..692802545 100644
--- a/sr_port/mu_swap_blk.c
+++ b/sr_port/mu_swap_blk.c
@@ -3,6 +3,9 @@
  * Copyright (c) 2001-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
+ * Copyright (c) 2023 YottaDB LLC and/or its subsidiaries.	*
+ * All rights reserved.						*
+ *								*
  *	This source code contains the intellectual property	*
  *	of its copyright holder(s), and is made available	*
  *	under a license.  If you do not know the terms of	*
@@ -79,6 +82,10 @@ GBLREF unsigned int	t_tries;
 GBLREF gv_key		*gv_currkey;
 GBLREF hash_table_int8	cw_stagnate;
 
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
 /******************************************************************************************
 Input Parameters:
 	level: level of working block
@@ -147,6 +154,13 @@ enum cdb_sc mu_swap_blk(int level, block_id *pdest_blk_id, kill_set *kill_set_pt
 	{
 		blk_was_free = FALSE;
 		INCR_BLK_NUM(dest_blk_id);
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP < dest_blk_id) && (dest_blk_id < ydb_skip_bml_num))
+		{
+			dest_blk_id = ydb_skip_bml_num;
+			continue;
+		}
+#		endif
 		/* A Pre-order traversal should not cause a child block to go to its parent.
 		 * However, in case it happens because already the organization was like that or for any other reason, skip swap.
 		 * If we decide to swap, code below should be changed to take care of the special case.
diff --git a/sr_port/mucregini.c b/sr_port/mucregini.c
index edcfe3e32..08008dbc3 100644
--- a/sr_port/mucregini.c
+++ b/sr_port/mucregini.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2019 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2019-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -68,6 +68,10 @@ GBLREF 	sgmnt_data_ptr_t	cs_data;
 GBLREF 	sgmnt_addrs		*cs_addrs;
 GBLREF	void			(*mupip_exit_fp)(int4 errnum);
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 error_def(ERR_COLLATIONUNDEF);
 error_def(ERR_COLLTYPVERSION);
 error_def(ERR_DBFILERR);
@@ -266,6 +270,11 @@ void mucregini(block_id blk_init_size)
 	NUM_CRIT_ENTRY(csd) = seg->mutex_slots;
 	csd->wcs_phase2_commit_wait_spincnt = WCS_PHASE2_COMMIT_DEFAULT_SPINCNT;
 	csd->defer_allocate = seg->defer_allocate;
+#	ifdef DEBUG
+	/* Force-enable DEFER_ALLOCATE in case ydb_skip_bml_num is non-zero to avoid huge test runtimes */
+	if (0 != ydb_skip_bml_num)
+		csd->defer_allocate = TRUE;
+#	endif
 	csd->read_only = seg->read_only;
 	time(&ctime);
 	assert(SIZEOF(ctime) >= SIZEOF(int4));
@@ -283,6 +292,10 @@ void mucregini(block_id blk_init_size)
 	bmm_init();
 	for (i = 0; i < blk_init_size ; i += csd->bplmap)
 	{
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (0 < i) && (i < ydb_skip_bml_num))
+			i = ydb_skip_bml_num;
+#		endif
 		status = bml_init(i);
 		if (status != SS_NORMAL)
 		{
diff --git a/sr_port/mupip_integ.c b/sr_port/mupip_integ.c
index b64b1f721..803d26520 100644
--- a/sr_port/mupip_integ.c
+++ b/sr_port/mupip_integ.c
@@ -117,7 +117,7 @@ GBLDEF global_list		*trees;
 GBLDEF sgmnt_data		mu_int_data;
 GBLDEF unsigned char		*mu_int_master;
 GBLDEF trans_num		largest_tn;
-GBLDEF int4			mu_int_blks_to_upgrd;
+GBLDEF block_id			mu_int_blks_to_upgrd;
 GBLDEF span_node_integ		*sndata;
 GBLDEF boolean_t		null_coll_type_err = FALSE;
 GBLDEF boolean_t		null_coll_type;
@@ -442,6 +442,13 @@ void mupip_integ(void)
 			 * verifications
 			 */
 			csd = &mu_int_data;
+#			ifdef DEBUG
+			fc = gv_cur_region->dyn.addr->file_cntl;
+			udi = FC2UDI(fc);
+			udi->s_addrs.hdr = csd;	/* Needed by asserts in "DB_LSEEKREAD" macro in "dbfilop()" calls when
+						 * "ydb_skip_bml_num" is non-zero.
+						 */
+#			endif
 		}
 		trees_tail = trees = (global_list *)malloc(SIZEOF(global_list));
 		memset(trees, 0, SIZEOF(global_list));
diff --git a/sr_port/muprec.h b/sr_port/muprec.h
index 65e90034a..8924d1197 100644
--- a/sr_port/muprec.h
+++ b/sr_port/muprec.h
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2018-2021 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2018-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -1282,7 +1282,7 @@ uint4			mur_back_phase1(reg_ctl_list *rctl);
 uint4			mur_back_phase2(reg_ctl_list *rctl);
 uint4			mur_back_processing_one_region(mur_back_opt_t *mur_back_options);
 int4 			mur_block_count_correct(reg_ctl_list *rctl);
-int4			mur_blocks_free(reg_ctl_list *rctl);
+block_id		mur_blocks_free(reg_ctl_list *rctl);
 boolean_t		mur_close_files(void);
 int4			mur_cre_file_extfmt(jnl_ctl_list *jctl, int recstat);
 void			mur_close_file_extfmt(boolean_t in_mur_close_files);
diff --git a/sr_port/mur_blocks_free.c b/sr_port/mur_blocks_free.c
index c86446003..bb4dbc896 100644
--- a/sr_port/mur_blocks_free.c
+++ b/sr_port/mur_blocks_free.c
@@ -3,6 +3,9 @@
  * Copyright (c) 2001-2021 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
+ * Copyright (c) 2023 YottaDB LLC and/or its subsidiaries.	*
+ * All rights reserved.						*
+ *								*
  *	This source code contains the intellectual property	*
  *	of its copyright holder(s), and is made available	*
  *	under a license.  If you do not know the terms of	*
@@ -38,16 +41,20 @@
 GBLREF	gd_region		*gv_cur_region;
 GBLREF	sgmnt_data_ptr_t	cs_data;
 
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
 #define BPL	SIZEOF(int4)*8/BML_BITS_PER_BLK					/* blocks masked by a int4 */
 
 error_def(ERR_DBRDERR);
 error_def(ERR_DYNUPGRDFAIL);
 
-int4 mur_blocks_free(reg_ctl_list *rctl)
+block_id mur_blocks_free(reg_ctl_list *rctl)
 {
 	int4		x;
-	block_id	bnum, maps;
-	int		mapsize, i, j, k, fcnt, status;
+	block_id	bnum, maps, i, fcnt;
+	int		mapsize, j, k, status;
 	unsigned char	*c, *disk, *m_ptr;
 	uint4		*dskmap, map_blk_size;
 	file_control	*db_ctl;
@@ -75,6 +82,14 @@ int4 mur_blocks_free(reg_ctl_list *rctl)
 	db_ctl->op_len = cs_data->blk_size;
 	for (i = 0; i != maps; i++)
 	{
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (1 == i))
+		{
+			i = ydb_skip_bml_num / BLKS_PER_LMAP - 1;
+			fcnt += (ydb_skip_bml_num - BLKS_PER_LMAP) / BLKS_PER_LMAP * (BLKS_PER_LMAP - 1);
+			continue;
+		}
+#		endif
 		bnum = i * cs_data->bplmap;
 		db_ctl->op = FC_READ;
 		db_ctl->op_pos = cs_data->start_vbn + ((gtm_int64_t)cs_data->blk_size / DISK_BLOCK_SIZE * bnum);
diff --git a/sr_port/mur_process_intrpt_recov.c b/sr_port/mur_process_intrpt_recov.c
index 43f82083b..0eaef7065 100644
--- a/sr_port/mur_process_intrpt_recov.c
+++ b/sr_port/mur_process_intrpt_recov.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2003-2017 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2018 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2018-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -63,7 +63,8 @@ uint4 mur_process_intrpt_recov()
 	char				prev_jnl_fn[MAX_FN_LEN + 1], rename_fn[MAX_FN_LEN + 1];
 	jnl_create_info			jnl_info;
 	uint4				status, status2;
-	uint4				max_autoswitchlimit, max_jnl_alq, max_jnl_deq, freeblks;
+	uint4				max_autoswitchlimit, max_jnl_alq, max_jnl_deq;
+	block_id			freeblks;
 	sgmnt_addrs			*csa;
 	sgmnt_data_ptr_t		csd;
 	jnl_private_control		*jpc;
diff --git a/sr_port/ydb_logicals_tab.h b/sr_port/ydb_logicals_tab.h
index 3060c70c0..e3452f08b 100644
--- a/sr_port/ydb_logicals_tab.h
+++ b/sr_port/ydb_logicals_tab.h
@@ -1,6 +1,6 @@
 /****************************************************************
  *								*
- * Copyright (c) 2018-2022 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2018-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -178,6 +178,7 @@ YDBENVINDX_TABLE_ENTRY (YDBENVINDX_DB_COUNTER_SEM_INCR,        "$ydb_db_counter_
 YDBENVINDX_TABLE_ENTRY (YDBENVINDX_DIRTREE_COLLHDR_ALWAYS,     "$ydb_dirtree_collhdr_always",     "$gtm_dirtree_collhdr_always")
 YDBENVINDX_TABLE_ENTRY (YDBENVINDX_GVUNDEF_FATAL,              "$ydb_gvundef_fatal",              "$gtm_gvundef_fatal")
 YDBENVINDX_TABLE_ENTRY (YDBENVINDX_LOCKHASH_N_BITS,            "$ydb_lockhash_n_bits",            "")
+YDBENVINDX_TABLE_ENTRY (YDBENVINDX_TEST_4G_DB_BLKS,            "$ydb_test_4g_db_blks",            "")
 YDBENVINDX_TABLE_ENTRY (YDBENVINDX_TEST_AUTORELINK_ALWAYS,     "$ydb_test_autorelink_always",     "$gtm_test_autorelink_always")
 YDBENVINDX_TABLE_ENTRY (YDBENVINDX_TEST_FAKE_ENOSPC,           "$ydb_test_fake_enospc",           "$gtm_test_fake_enospc")
 YDBENVINDX_TABLE_ENTRY (YDBENVINDX_TEST_JNLPOOL_SYNC,          "$ydb_test_jnlpool_sync",          "$gtm_test_jnlpool_sync")
diff --git a/sr_unix/db_write_eof_block.c b/sr_unix/db_write_eof_block.c
index 1e5c56e23..000317d72 100644
--- a/sr_unix/db_write_eof_block.c
+++ b/sr_unix/db_write_eof_block.c
@@ -3,6 +3,9 @@
  * Copyright (c) 2016 Fidelity National Information		*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
+ * Copyright (c) 2023 YottaDB LLC and/or its subsidiaries.	*
+ * All rights reserved.						*
+ *								*
  *	This source code contains the intellectual property	*
  *	of its copyright holder(s), and is made available	*
  *	under a license.  If you do not know the terms of	*
@@ -25,6 +28,10 @@
 #include "gtmio.h"
 #include "anticipatory_freeze.h"
 
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
 /* #GTM_THREAD_SAFE : The below function db_write_eof_block is thread-safe */
 int	db_write_eof_block(unix_db_info *udi, int fd, int blk_size, off_t offset, dio_buff_t *diobuff)
 {
@@ -48,7 +55,21 @@ int	db_write_eof_block(unix_db_info *udi, int fd, int blk_size, off_t offset, di
 	{
 		csa = &udi->s_addrs;
 		assert(fd == udi->fd);
+#		ifdef DEBUG
+		block_id	save_ydb_skip_bml_num;
+
+		/* It is possible we write an EOF block to the offset corresponding to bitmap block BLKS_PER_LMAP. In that case,
+		 * we want to disable the "ydb_skip_bml_num" related assert in DB_LSEEKWRITE. We do that by resetting
+		 * "ydb_skip_bml_num" to 0 in that case.
+		 */
+		save_ydb_skip_bml_num = ydb_skip_bml_num;
+		if (offset == (BLK_ZERO_OFF(udi->s_addrs.hdr->start_vbn) + (BLKS_PER_LMAP * udi->s_addrs.hdr->blk_size)))
+			ydb_skip_bml_num = 0;
+#		endif
 		DB_LSEEKWRITE(csa, udi, udi->fn, fd, offset, buff, blk_size, status);
+#		ifdef DEBUG
+		ydb_skip_bml_num = save_ydb_skip_bml_num;	/* restore "ydb_skip_bml_num" in case it got reset */
+#		endif
 	} else
 		DB_LSEEKWRITE(NULL, ((unix_db_info *)NULL), NULL, fd, offset, buff, blk_size, status);
 	if (free_needed)
diff --git a/sr_unix/dsk_read.c b/sr_unix/dsk_read.c
index 5f78dc326..b620a1b52 100644
--- a/sr_unix/dsk_read.c
+++ b/sr_unix/dsk_read.c
@@ -65,6 +65,10 @@ GBLREF	jnl_gbls_t		jgbl;
 GBLREF	uint4			process_id;
 GBLREF	uint4			mu_reorg_encrypt_in_prog;
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 error_def(ERR_DYNUPGRDFAIL);
 
 int4	dsk_read (block_id blk, sm_uc_ptr_t buff, enum db_ver *ondsk_blkver, boolean_t blk_free)
@@ -121,6 +125,18 @@ int4	dsk_read (block_id blk, sm_uc_ptr_t buff, enum db_ver *ondsk_blkver, boolea
 	assert(csd == cs_data);
 	size = csd->blk_size;
 	assert(csd->acc_meth == dba_bg);
+#	ifdef DEBUG
+	if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= blk) && (blk < ydb_skip_bml_num))
+	{	/* Huge db scheme is in effect and a block in the range of the HOLE in the huge db (any block
+		 * number from the bitmap block BLKS_PER_LMAP to block "ydb_skip_bml_num-1") was specified. This is possible
+		 * in case of a restartable transaction situation. In this case, just return a zeroed block and the
+		 * transaction will eventually restart.
+		 */
+		memset(buff, 0, size);
+		in_dsk_read--;
+		return 0;
+	}
+#	endif
 	/* Since csd->fully_upgraded is referenced more than once in this module (once explicitly and once in
 	 * GDS_BLK_UPGRADE_IF_NEEDED macro used below), take a copy of it and use that so all usages see the same value.
 	 * Not doing this, for example, can cause us to see the database as fully upgraded in the first check causing us
diff --git a/sr_unix/gdsfilext.c b/sr_unix/gdsfilext.c
index 942b0496b..4950c9574 100644
--- a/sr_unix/gdsfilext.c
+++ b/sr_unix/gdsfilext.c
@@ -81,7 +81,15 @@ MBSTART {															\
 			2, LEN_AND_LIT("Please make more disk space available or shutdown GT.M to avoid data loss"), ENOSPC);	\
 } MBEND
 
-#define SUSPICIOUS_EXTEND 	(2 * (dollar_tlevel ? sgm_info_ptr->cw_set_depth : cw_set_depth) < cs_addrs->ti->free_blocks)
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
+#define SUSPICIOUS_EXTEND 	((2 * (dollar_tlevel ? sgm_info_ptr->cw_set_depth : cw_set_depth)				\
+					DEBUG_ONLY( + ((0 != ydb_skip_bml_num)							\
+						? ((ydb_skip_bml_num - BLKS_PER_LMAP) / BLKS_PER_LMAP * (BLKS_PER_LMAP - 1))	\
+						: 0)))										\
+					< cs_addrs->ti->free_blocks)								\
 
 GBLREF	sigset_t		blockalrm;
 GBLREF	sgmnt_addrs		*cs_addrs;
@@ -100,6 +108,10 @@ GBLREF	boolean_t		ydb_dbfilext_syslog_disable;	/* control whether db file extens
 GBLREF	uint4			ydbDebugLevel;
 GBLREF	jnlpool_addrs_ptr_t	jnlpool;
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 error_def(ERR_DBFILERR);
 error_def(ERR_DBFILEXT);
 error_def(ERR_DSKSPACEFLOW);
@@ -183,6 +195,14 @@ int4 gdsfilext(block_id blocks, block_id filesize, boolean_t trans_in_prog)
 			- DIVIDE_ROUND_UP(cs_data->trans_hist.total_blks, bplmap) + blocks, bplmap - 1)
 			- DIVIDE_ROUND_UP(cs_data->trans_hist.total_blks, bplmap);
 	new_blocks = blocks + new_bit_maps;
+#	ifdef DEBUG
+	if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP >= cs_data->trans_hist.total_blks)
+			&& (BLKS_PER_LMAP < (cs_data->trans_hist.total_blks + new_blocks)))
+	{
+		new_blocks += (ydb_skip_bml_num - BLKS_PER_LMAP);
+		new_bit_maps += (ydb_skip_bml_num - BLKS_PER_LMAP) / BLKS_PER_LMAP;
+	}
+#	endif
 	assert((0 < new_blocks) || (!cs_data->defer_allocate && (0 == new_blocks)));
 	if (new_blocks + cs_data->trans_hist.total_blks > MAXTOTALBLKS(cs_data))
 	{
@@ -196,6 +216,10 @@ int4 gdsfilext(block_id blocks, block_id filesize, boolean_t trans_in_prog)
 		RTS_ERROR_CSA_ABT(cs_addrs, VARLSTCNT(5) ERR_DBFILERR, 2, DB_LEN_STR(gv_cur_region), save_errno);
 	} else
 	{
+#		ifdef DEBUG
+		if (0 == ydb_skip_bml_num)
+		{
+#		endif
 		if (!(ydbDebugLevel & GDL_IgnoreAvailSpace))
 		{	/* Bypass this space check if debug flag above is on. Allows us to create a large sparce DB
 			 * in space it could never fit it if wasn't sparse. Needed for some tests.
@@ -218,6 +242,9 @@ int4 gdsfilext(block_id blocks, block_id filesize, boolean_t trans_in_prog)
 				}
 			}
 		}
+#		ifdef DEBUG
+		}
+#		endif
 	}
 #	ifdef DEBUG
 	if ( (WBTEST_ENABLED(WBTEST_MM_CONCURRENT_FILE_EXTEND) && dollar_tlevel && !MEMCMP_LIT(gv_cur_region->rname, "DEFAULT")) ||
@@ -482,6 +509,11 @@ int4 gdsfilext(block_id blocks, block_id filesize, boolean_t trans_in_prog)
 		for (map = ROUND_UP(old_total, bplmap); map < new_total; map += bplmap)
 		{
 			DEBUG_ONLY(new_bit_maps--;)
+#			ifdef DEBUG
+			assert(0 < map);
+			if ((0 != ydb_skip_bml_num) && (map < ydb_skip_bml_num))
+				continue;
+#			endif
 			if (SS_NORMAL != (status = bml_init(map)))
 			{
 				GDSFILEXT_CLNUP;
@@ -519,6 +551,11 @@ int4 gdsfilext(block_id blocks, block_id filesize, boolean_t trans_in_prog)
 	assert(cs_data->blks_to_upgrd == (inctn_detail.blks2upgrd_struct.blks_to_upgrd_delta + prev_extend_blks_to_upgrd));
 	assert((0 < blocks) || (!cs_data->defer_allocate && (0 == new_blocks)));
 	assert(0 < (cs_addrs->ti->free_blocks + blocks));
+#	ifdef DEBUG
+	if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP >= cs_data->trans_hist.total_blks)
+				&& (BLKS_PER_LMAP < (cs_data->trans_hist.total_blks + new_blocks)))
+		blocks += (ydb_skip_bml_num - BLKS_PER_LMAP) / BLKS_PER_LMAP * (BLKS_PER_LMAP - 1);
+#	endif
 	cs_addrs->ti->free_blocks += blocks;
 	cs_addrs->total_blks = cs_addrs->ti->total_blks = new_total;
 	blocks = old_total;
diff --git a/sr_unix/gdsfilext_nojnl.c b/sr_unix/gdsfilext_nojnl.c
index 2abb309d3..f3acc8ecd 100644
--- a/sr_unix/gdsfilext_nojnl.c
+++ b/sr_unix/gdsfilext_nojnl.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2012-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2019 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2019-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -62,6 +62,10 @@
 
 GBLREF	jnl_gbls_t	jgbl;
 
+#ifdef DEBUG
+GBLREF	block_id	ydb_skip_bml_num;
+#endif
+
 error_def(ERR_DBFILERR);
 
 /* Minimal file extend. Called (at the moment) from mur_back_process.c when processing JRT_TRUNC record.
@@ -126,6 +130,11 @@ int gdsfilext_nojnl(gd_region* reg, block_id new_total, block_id old_total)
 	/* initialize bitmaps, if any new ones are added */
 	for (ii = ROUND_UP(old_total, BLKS_PER_LMAP); ii < new_total; ii += BLKS_PER_LMAP)
 	{
+#		ifdef DEBUG
+		assert(0 < ii);
+		if ((0 != ydb_skip_bml_num) && (ii < ydb_skip_bml_num))
+			continue;
+#		endif
 		offset = (off_t)BLK_ZERO_OFF(csd->start_vbn) + (off_t)ii * blk_size;
 		DB_LSEEKWRITE(csa, udi, udi->fn, udi->fd, offset, aligned_buff, blk_size, status);
 		if (0 != status)
diff --git a/sr_unix/gtmio.h b/sr_unix/gtmio.h
index a5b3d4c4a..1101e8174 100644
--- a/sr_unix/gtmio.h
+++ b/sr_unix/gtmio.h
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2018 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2018-2021 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2018-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -384,10 +384,19 @@ MBSTART {											\
 		RC = -1;		/* Something kept us from reading what we wanted */	\
 } MBEND
 
-#define	DB_LSEEKREAD(UDI, FD, OFFSET, BUFF, SIZE, STATUS)		\
-MBSTART {								\
-	DBG_CHECK_DIO_ALIGNMENT(UDI, OFFSET, BUFF, SIZE);		\
-	LSEEKREAD(FD, OFFSET, BUFF, SIZE, STATUS);			\
+#ifdef DEBUG
+GBLREF	gtm_int8	ydb_skip_bml_num;	/* Use "gtm_int8" since it is possible "block_id" type is not yet defined */
+#endif
+
+#define	DB_LSEEKREAD(UDI, FD, OFFSET, BUFF, SIZE, STATUS)							\
+MBSTART {													\
+	DBG_CHECK_DIO_ALIGNMENT(UDI, OFFSET, BUFF, SIZE);							\
+	assert((0 == ydb_skip_bml_num) || (0 == OFFSET) || (NULL == ((unix_db_info *)UDI)->s_addrs.hdr)		\
+		|| ((BLK_ZERO_OFF(((unix_db_info *)UDI)->s_addrs.hdr->start_vbn)				\
+			+ ((gtm_int8)BLKS_PER_LMAP * ((unix_db_info *)UDI)->s_addrs.hdr->blk_size)) > OFFSET)	\
+		|| ((BLK_ZERO_OFF(((unix_db_info *)UDI)->s_addrs.hdr->start_vbn)				\
+			+ (ydb_skip_bml_num * ((unix_db_info *)UDI)->s_addrs.hdr->blk_size)) <= OFFSET));	\
+	LSEEKREAD(FD, OFFSET, BUFF, SIZE, STATUS);					\
 } MBEND
 
 /* The below macro is almost the same as LSEEKREAD except it has an extra parameter where the number of
diff --git a/sr_unix/mu_cre_file.c b/sr_unix/mu_cre_file.c
index 25cefdc24..31eb1a12f 100644
--- a/sr_unix/mu_cre_file.c
+++ b/sr_unix/mu_cre_file.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2021 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2018-2022 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2018-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -128,6 +128,7 @@ GBLREF	sgmnt_data_ptr_t	cs_data;
 GBLREF	uint4			ydbDebugLevel;
 #ifdef DEBUG
 GBLREF	boolean_t		in_mu_cre_file;
+GBLREF	block_id		ydb_skip_bml_num;
 #endif
 
 STATICDEF	int	mu_cre_file_fd;		/* needed for "mu_cre_file_ch" */
@@ -403,6 +404,10 @@ unsigned char mu_cre_file(boolean_t caller_is_mupip_create)
 	 * manner as every non-bitmap block must have an associated bitmap)
 	 */
 	cs_data->trans_hist.total_blks += DIVIDE_ROUND_UP(cs_data->trans_hist.total_blks, BLKS_PER_LMAP - 1);
+#	ifdef DEBUG
+	if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP < cs_data->trans_hist.total_blks))
+		cs_data->trans_hist.total_blks += (ydb_skip_bml_num - BLKS_PER_LMAP);
+#	endif
 	cs_data->extension_size = gv_cur_region->dyn.addr->ext_blk_count;
 	/* Check if this file is an encrypted database. If yes, do init */
 	if (IS_ENCRYPTED(gv_cur_region->dyn.addr->is_encrypted))
@@ -454,6 +459,7 @@ unsigned char mu_cre_file(boolean_t caller_is_mupip_create)
 	}
 	if (!cs_data->defer_allocate)
 	{
+		assert(0 == ydb_skip_bml_num);
 		status = posix_fallocate(udi->fd, 0, BLK_ZERO_OFF(cs_data->start_vbn) +
 					 ((off_t)(cs_data->trans_hist.total_blks + 1) * cs_data->blk_size));
 		if (0 != status)
diff --git a/sr_unix/mu_swap_root.c b/sr_unix/mu_swap_root.c
index 60c1ff4f2..d78ae1f81 100644
--- a/sr_unix/mu_swap_root.c
+++ b/sr_unix/mu_swap_root.c
@@ -79,6 +79,10 @@ GBLREF	unsigned char		cw_set_depth;
 GBLREF	unsigned char		rdfail_detail;
 GBLREF	unsigned int		t_tries;
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 #define RETRY_SWAP		(0)
 #define ABORT_SWAP		(1)
 
@@ -306,6 +310,17 @@ block_id swap_root_or_directory_block(int parent_blk_lvl, int child_blk_lvl, src
 		t_abort(gv_cur_region, csa);
 		return ABORT_SWAP;
 	}
+#	ifdef DEBUG
+	if ((0 != ydb_skip_bml_num) && (1 == master_bit))
+	{
+		master_bit = bmm_find_free(ydb_skip_bml_num / BLKS_PER_LMAP, csa->bmm, num_local_maps);
+		if ((NO_FREE_SPACE == master_bit) || (1 == master_bit))
+		{
+			t_abort(gv_cur_region, csa);
+			return ABORT_SWAP;
+		}
+	}
+#	endif
 	bmlhist.blk_num = master_bit * BLKS_PER_LMAP;
 	if (NULL == (bmlhist.buffaddr = t_qread(bmlhist.blk_num, (sm_int_ptr_t)&bmlhist.cycle, &bmlhist.cr)))
 	{
diff --git a/sr_unix/mu_truncate.c b/sr_unix/mu_truncate.c
index 187f226f4..9582aefb3 100644
--- a/sr_unix/mu_truncate.c
+++ b/sr_unix/mu_truncate.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2012-2021 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2019-2022 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2019-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -213,6 +213,10 @@ boolean_t mu_truncate(int4 truncate_percent, mval *keep_mval)
 			return TRUE;
 		}
 		lmap_blk_num = lmap_num * BLKS_PER_LMAP;
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= lmap_blk_num) && (lmap_blk_num < ydb_skip_bml_num))
+			break;
+#		endif
 		if (csa->nl->highest_lbm_with_busy_blk >= lmap_blk_num)
 		{
 			found_busy_blk = lmap_blk_num;
diff --git a/sr_unix/mubinccpy.c b/sr_unix/mubinccpy.c
index 610f11aac..fa29e9c57 100644
--- a/sr_unix/mubinccpy.c
+++ b/sr_unix/mubinccpy.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2020 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2020-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -333,6 +333,13 @@ bool	mubinccpy (backup_reg_list *list)
 	read_offset = (off_t)BLK_ZERO_OFF(header->start_vbn);
 	for (blk_num_base = 0;  blk_num_base < header->trans_hist.total_blks;  blk_num_base += blks_per_buff)
 	{
+#		ifdef DEBUG
+		if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= blk_num_base) && (blk_num_base < ydb_skip_bml_num))
+		{
+			read_offset += (bsize * (ydb_skip_bml_num - blk_num_base));
+			blk_num_base = ydb_skip_bml_num;
+		}
+#		endif
 		if (online && (0 != cs_addrs->shmpool_buffer->failed))
 			break;
 		if ((header->trans_hist.total_blks - blk_num_base) < blks_per_buff)
@@ -364,6 +371,10 @@ bool	mubinccpy (backup_reg_list *list)
 		for (i = 0; i < blks_per_buff; i++, bptr = (blk_hdr *)((char *)bptr + bsize))
 		{
 			blk_num = blk_num_base + i;
+#			ifdef DEBUG
+			if ((0 != ydb_skip_bml_num) && (BLKS_PER_LMAP <= blk_num) && (blk_num < ydb_skip_bml_num))
+				continue;
+#			endif
 			if (mu_ctrly_occurred  ||  mu_ctrlc_occurred)
 			{
 				free(outptr);
diff --git a/sr_unix/mupip_restore.c b/sr_unix/mupip_restore.c
index d603e4b41..04b60a92a 100644
--- a/sr_unix/mupip_restore.c
+++ b/sr_unix/mupip_restore.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2019-2022 YottaDB LLC and/or its subsidiaries.	*
+ * Copyright (c) 2019-2023 YottaDB LLC and/or its subsidiaries.	*
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -81,6 +81,10 @@ GBLREF	uint4			pipe_child;
 GBLREF	gd_region		*gv_cur_region;
 GBLREF	int4			restore_read_errno;
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 LITREF	char			*gtm_dbversion_table[];
 LITREF	char			*mdb_ver_names[];
 
@@ -213,6 +217,11 @@ void mupip_restore(void)
 	}
 	if (udi->fd_opened_with_o_direct)
 		memcpy(&old_data, csd, SGMNT_HDR_LEN);
+#	ifdef DEBUG
+	udi->s_addrs.hdr = &old_data;	/* Now that we have read in the file header, point udi to it for the next dbfilop.
+					 * This is used by the DB_LSEEKREAD macro if "ydb_skip_bml_num" is non-zero.
+					 */
+#	endif
 	if (memcmp(old_data.label, label, GDS_LABEL_SZ) && memcmp(old_data.label, v6_label, GDS_LABEL_SZ))
 	{
 		util_out_print("Output file !AD has an unrecognizable format", TRUE, n_len, db_name);
@@ -421,6 +430,11 @@ void mupip_restore(void)
 				 */
 				new_eof = (off_t)BLK_ZERO_OFF(old_start_vbn) + ((off_t)inhead.db_total_blks * old_blk_size);
 				new_size = new_eof + old_blk_size;
+#				ifdef DEBUG
+				udi->s_addrs.hdr = csd;	/* Point udi to an up to date file header as it is used by the below
+							 * "db_write_eof_block()" call if "ydb_skip_bml_num" is non-zero.
+							 */
+#				endif
 				status = db_write_eof_block(udi, db_fd, old_blk_size, new_eof, &(TREF(dio_buff)));
 				if (0 != status)
 				{
@@ -496,6 +510,10 @@ void mupip_restore(void)
 					bml_newmap((blk_hdr_ptr_t)newmap, BM_SIZE(bplmap), curr_tn, csd->desired_db_format);
 					for (ii = ROUND_UP(old_tot_blks, bplmap); ii < inhead.db_total_blks; ii += bplmap)
 					{
+#						ifdef DEBUG
+						if ((0 != ydb_skip_bml_num) && (0 < ii) && (ii < ydb_skip_bml_num))
+							ii = ydb_skip_bml_num;
+#						endif
 						offset = (off_t)BLK_ZERO_OFF(old_start_vbn) + (off_t)ii * old_blk_size;
 						DB_LSEEKWRITE(NULL, udi, NULL, db_fd, offset, newmap, old_blk_size, status);
 						if (0 != status)
diff --git a/sr_unix/warn_db_sz.c b/sr_unix/warn_db_sz.c
index ecdeecd15..c29087503 100644
--- a/sr_unix/warn_db_sz.c
+++ b/sr_unix/warn_db_sz.c
@@ -3,6 +3,9 @@
  * Copyright (c) 2018-2020 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
+ * Copyright (c) 2023 YottaDB LLC and/or its subsidiaries.	*
+ * All rights reserved.						*
+ *								*
  *	This source code contains the intellectual property	*
  *	of its copyright holder(s), and is made available	*
  *	under a license.  If you do not know the terms of	*
@@ -22,12 +25,20 @@
 
 error_def(ERR_LOWSPC);
 
+#ifdef DEBUG
+GBLREF	block_id		ydb_skip_bml_num;
+#endif
+
 void warn_db_sz(char *db_fname, block_id prev_blocks, block_id curr_blocks, block_id tot_blocks)
 {
 	double new_sz_frac;
 	double old_sz_frac;
 	int diff;
 
+#	ifdef DEBUG
+	if (0 != ydb_skip_bml_num)
+		return;	/* Do not issue LOWSPC warning if huge sparse dbs are possible */
+#	endif
 	new_sz_frac = (WBTEST_ENABLED(WBTEST_DB_BLOCKS_WARN)) ?
 			SPCWARNTHRESHOLD : (((double)curr_blocks) / ((double)tot_blocks)) * 100;
 	if (new_sz_frac < SPCWARNTHRESHOLD)