diff --git a/src/jrd/btr.cpp b/src/jrd/btr.cpp
index 71d5e6224cd..e9978fd4169 100644
--- a/src/jrd/btr.cpp
+++ b/src/jrd/btr.cpp
@@ -924,12 +924,12 @@ bool BTR_delete_index(thread_db* tdbb, WIN* window, USHORT id)
 	{
 		index_root_page::irt_repeat* irt_desc = root->irt_rpt + id;
 		CCH_MARK(tdbb, window);
-		const PageNumber next(window->win_page.getPageSpaceID(), irt_desc->getRoot());
-		tree_exists = (irt_desc->getRoot() != 0);
+		const ULONG rootPage = irt_desc->getRoot();
+		const PageNumber next(window->win_page.getPageSpaceID(), rootPage);
+		tree_exists = (rootPage != 0);
 
 		// remove the pointer to the top-level index page before we delete it
-		irt_desc->setRoot(0);
-		irt_desc->irt_flags = 0;
+		irt_desc->setEmpty();
 		const PageNumber prior = window->win_page;
 		const USHORT relation_id = root->irt_relation;
 
@@ -962,11 +962,12 @@ bool BTR_description(thread_db* tdbb, jrd_rel* relation, index_root_page* root,
 
 	const index_root_page::irt_repeat* irt_desc = &root->irt_rpt[id];
 
-	if (irt_desc->getRoot() == 0)
+	const ULONG rootPage = irt_desc->getRoot();
+	if (!rootPage)
 		return false;
 
 	idx->idx_id = id;
-	idx->idx_root = irt_desc->getRoot();
+	idx->idx_root = rootPage;
 	idx->idx_count = irt_desc->irt_keys;
 	idx->idx_flags = irt_desc->irt_flags;
 	idx->idx_runtime_flags = 0;
@@ -2124,18 +2125,18 @@ bool BTR_next_index(thread_db* tdbb, jrd_rel* relation, jrd_tra* transaction, in
 	for (; id < root->irt_count; ++id)
 	{
 		const index_root_page::irt_repeat* irt_desc = root->irt_rpt + id;
-		if (irt_desc->getTransaction() && transaction)
+		const TraNumber inProgressTrans = irt_desc->inProgress();
+		if (inProgressTrans && transaction)
 		{
-			const TraNumber trans = irt_desc->getTransaction();
 			CCH_RELEASE(tdbb, window);
-			const int trans_state = TRA_wait(tdbb, transaction, trans, jrd_tra::tra_wait);
+			const int trans_state = TRA_wait(tdbb, transaction, inProgressTrans, jrd_tra::tra_wait);
 			if ((trans_state == tra_dead) || (trans_state == tra_committed))
 			{
 				// clean up this left-over index
 				root = (index_root_page*) CCH_FETCH(tdbb, window, LCK_write, pag_root);
 				irt_desc = root->irt_rpt + id;
 
-				if (irt_desc->getTransaction() == trans)
+				if (irt_desc->inProgress() == inProgressTrans)
 					BTR_delete_index(tdbb, window, id);
 				else
 					CCH_RELEASE(tdbb, window);
@@ -2359,7 +2360,7 @@ void BTR_reserve_slot(thread_db* tdbb, IndexCreation& creation)
 	fb_assert(idx->idx_count <= MAX_UCHAR);
 	slot->irt_keys = (UCHAR) idx->idx_count;
 	slot->irt_flags = idx->idx_flags;
-	slot->setTransaction(transaction->tra_number);
+	slot->setInProgress(transaction->tra_number);
 
 	// Exploit the fact idx_repeat structure matches ODS IRTD one
 	memcpy(desc, idx->idx_rpt, len);
@@ -2393,13 +2394,13 @@ void BTR_selectivity(thread_db* tdbb, jrd_rel* relation, USHORT id, SelectivityL
 	if (!root)
 		return;
 
-	ULONG page;
-	if (id >= root->irt_count || !(page = root->irt_rpt[id].getRoot()))
+	if (id >= root->irt_count || !root->irt_rpt[id].getRoot())
 	{
 		CCH_RELEASE(tdbb, &window);
 		return;
 	}
 
+	ULONG page = root->irt_rpt[id].getRoot();
 	const bool descending = (root->irt_rpt[id].irt_flags & irt_descending);
 	const ULONG segments = root->irt_rpt[id].irt_keys;
 
diff --git a/src/jrd/btr.h b/src/jrd/btr.h
index 7f1bc99303e..7a636e866f4 100644
--- a/src/jrd/btr.h
+++ b/src/jrd/btr.h
@@ -58,7 +58,7 @@ struct index_desc
 	ULONG	idx_root;						// Index root
 	float	idx_selectivity;				// selectivity of index
 	USHORT	idx_id;
-	UCHAR	idx_flags;
+	USHORT	idx_flags;
 	UCHAR	idx_runtime_flags;				// flags used at runtime, not stored on disk
 	USHORT	idx_primary_index;				// id for primary key partner index
 	USHORT	idx_primary_relation;			// id for primary key partner relation
diff --git a/src/jrd/idx.h b/src/jrd/idx.h
index 3fd62251440..dd094798182 100644
--- a/src/jrd/idx.h
+++ b/src/jrd/idx.h
@@ -36,7 +36,7 @@ struct ini_idx_t
 {
 	UCHAR ini_idx_index_id;
 	UCHAR ini_idx_relid;
-	UCHAR ini_idx_flags;
+	USHORT ini_idx_flags;
 	UCHAR ini_idx_segment_count;
 	USHORT ini_idx_ods;
 	struct ini_idx_segment_t
diff --git a/src/jrd/ini.epp b/src/jrd/ini.epp
index d0d6527971b..cba8b9d83d5 100644
--- a/src/jrd/ini.epp
+++ b/src/jrd/ini.epp
@@ -1636,7 +1636,7 @@ static void store_indices(thread_db* tdbb, USHORT odsVersion)
 			PAD(relation->rel_name, X.RDB$RELATION_NAME);
 			PAD(indexName, X.RDB$INDEX_NAME);
 
-			X.RDB$UNIQUE_FLAG = index->ini_idx_flags & idx_unique;
+			X.RDB$UNIQUE_FLAG = (index->ini_idx_flags & idx_unique) ? 1 : 0;
 			X.RDB$SEGMENT_COUNT = index->ini_idx_segment_count;
 
 			if (index->ini_idx_flags & idx_descending)
diff --git a/src/jrd/ods.h b/src/jrd/ods.h
index 12d40717108..40d0b8de814 100644
--- a/src/jrd/ods.h
+++ b/src/jrd/ods.h
@@ -365,42 +365,50 @@ struct index_root_page
 {
 	pag irt_header;
 	USHORT irt_relation;			// relation id (for consistency)
-	USHORT irt_count;				// Number of indices
+	USHORT irt_count;				// number of indices
+	ULONG irt_unused;				// so far used as a padding to ensure the same
+									// alignment between 32-bit and 64-bit builds
 	struct irt_repeat
 	{
+		friend class index_root_page;	// to allow offset check for private members
 	private:
-		friend struct index_root_page; // to allow offset check for private members
-		ULONG irt_root;				// page number of index root if irt_in_progress is NOT set, or
-									// highest 32 bit of transaction if irt_in_progress is set
-		ULONG irt_transaction;		// transaction in progress (lowest 32 bits)
+		union
+		{
+			FB_UINT64 irt_transaction;	// transaction in progress
+			struct
+			{
+				ULONG irt_page_num;			// page number
+				ULONG irt_page_space_id;	// page space
+			} irt_root;						// index root page
+		};
 	public:
-		USHORT irt_desc;			// offset to key descriptions
-		UCHAR irt_keys;				// number of keys in index
-		UCHAR irt_flags;
+		USHORT irt_desc;				// offset to key descriptions
+		USHORT irt_flags;				// index flags
+		UCHAR irt_keys;					// number of keys in index
 
-		ULONG getRoot() const;
-		void setRoot(ULONG root_page);
+		TraNumber inProgress() const;
+		void setInProgress(TraNumber traNumber);
 
-		TraNumber getTransaction() const;
-		void setTransaction(TraNumber traNumber);
+		ULONG getRoot() const;
+		void setRoot(ULONG rootPage);
 
 		bool isUsed() const;
-
+		void setEmpty();
 	} irt_rpt[1];
 
-	static_assert(sizeof(struct irt_repeat) == 12, "struct irt_repeat size mismatch");
+	static_assert(sizeof(struct irt_repeat) == 16, "struct irt_repeat size mismatch");
+	static_assert(offsetof(struct irt_repeat, irt_transaction) == 0, "irt_transaction offset mismatch");
 	static_assert(offsetof(struct irt_repeat, irt_root) == 0, "irt_root offset mismatch");
-	static_assert(offsetof(struct irt_repeat, irt_transaction) == 4, "irt_transaction offset mismatch");
 	static_assert(offsetof(struct irt_repeat, irt_desc) == 8, "irt_desc offset mismatch");
-	static_assert(offsetof(struct irt_repeat, irt_keys) == 10, "irt_keys offset mismatch");
-	static_assert(offsetof(struct irt_repeat, irt_flags) == 11, "irt_flags offset mismatch");
+	static_assert(offsetof(struct irt_repeat, irt_flags) == 10, "irt_flags offset mismatch");
+	static_assert(offsetof(struct irt_repeat, irt_keys) == 12, "irt_keys offset mismatch");
 };
 
-static_assert(sizeof(struct index_root_page) == 32, "struct index_root_page size mismatch");
+static_assert(sizeof(struct index_root_page) == 40, "struct index_root_page size mismatch");
 static_assert(offsetof(struct index_root_page, irt_header) == 0, "irt_header offset mismatch");
 static_assert(offsetof(struct index_root_page, irt_relation) == 16, "irt_relation offset mismatch");
 static_assert(offsetof(struct index_root_page, irt_count) == 18, "irt_count offset mismatch");
-static_assert(offsetof(struct index_root_page, irt_rpt) == 20, "irt_rpt offset mismatch");
+static_assert(offsetof(struct index_root_page, irt_rpt) == 24, "irt_rpt offset mismatch");
 
 // key descriptor
 
@@ -425,32 +433,39 @@ inline constexpr USHORT irt_primary			= 16;
 inline constexpr USHORT irt_expression		= 32;
 inline constexpr USHORT irt_condition		= 64;
 
-inline ULONG index_root_page::irt_repeat::getRoot() const
+inline bool index_root_page::irt_repeat::isUsed() const
 {
-	return (irt_flags & irt_in_progress) ? 0 : irt_root;
+	return (irt_flags & irt_in_progress) || (irt_root.irt_page_num != 0);
 }
 
-inline void index_root_page::irt_repeat::setRoot(ULONG root_page)
+inline void index_root_page::irt_repeat::setEmpty()
 {
-	irt_root = root_page;
-	irt_flags &= ~irt_in_progress;
+	irt_transaction = 0;
+	fb_assert(irt_root.irt_page_num == 0 && irt_root.irt_page_space_id == 0);
+	irt_flags = 0;
 }
 
-inline TraNumber index_root_page::irt_repeat::getTransaction() const
+inline TraNumber index_root_page::irt_repeat::inProgress() const
 {
-	return (irt_flags & irt_in_progress) ? ((TraNumber) irt_root << BITS_PER_LONG) | irt_transaction : 0;
+	return (irt_flags & irt_in_progress) ? irt_transaction : 0;
 }
 
-inline void index_root_page::irt_repeat::setTransaction(TraNumber traNumber)
+inline void index_root_page::irt_repeat::setInProgress(TraNumber traNumber)
 {
-	irt_root = ULONG(traNumber >> BITS_PER_LONG);
-	irt_transaction = ULONG(traNumber);
+	irt_transaction = traNumber;
 	irt_flags |= irt_in_progress;
 }
 
-inline bool index_root_page::irt_repeat::isUsed() const
+inline ULONG index_root_page::irt_repeat::getRoot() const
+{
+	return (irt_flags & irt_in_progress) ? 0 : irt_root.irt_page_num;
+}
+
+inline void index_root_page::irt_repeat::setRoot(ULONG rootPage)
 {
-	return (irt_flags & irt_in_progress) || (irt_root != 0);
+	irt_root.irt_page_num = rootPage;
+	irt_root.irt_page_space_id = 0;
+	irt_flags &= ~irt_in_progress;
 }
 
 
diff --git a/src/jrd/validation.cpp b/src/jrd/validation.cpp
index ec0f4981771..dfdd5ec7328 100644
--- a/src/jrd/validation.cpp
+++ b/src/jrd/validation.cpp
@@ -1956,7 +1956,7 @@ void Validation::walk_generators()
 	}
 }
 
-Validation::RTN Validation::walk_index(jrd_rel* relation, index_root_page& root_page, USHORT id)
+Validation::RTN Validation::walk_index(jrd_rel* relation, index_root_page* root_page, USHORT id)
 {
 /**************************************
  *
@@ -1976,25 +1976,24 @@ Validation::RTN Validation::walk_index(jrd_rel* relation, index_root_page& root_
  **************************************/
 	Database* dbb = vdr_tdbb->getDatabase();
 
-	const ULONG page_number = root_page.irt_rpt[id].getRoot();
-	if (!page_number) {
+	const ULONG page_number = root_page->irt_rpt[id].getRoot();
+	if (!page_number)
 		return rtn_ok;
-	}
 
-	const bool unique = (root_page.irt_rpt[id].irt_flags & (irt_unique | idx_primary));
-	const bool descending = (root_page.irt_rpt[id].irt_flags & irt_descending);
-	const bool condition = (root_page.irt_rpt[id].irt_flags & irt_condition);
+	const bool unique = (root_page->irt_rpt[id].irt_flags & (irt_unique | idx_primary));
+	const bool descending = (root_page->irt_rpt[id].irt_flags & irt_descending);
+	const bool condition = (root_page->irt_rpt[id].irt_flags & irt_condition);
 
-	temporary_key nullKey, *null_key = 0;
+	temporary_key nullKey, *null_key = nullptr;
 	if (unique)
 	{
 		index_desc idx;
 		{
 			// No need to evaluate index expression and/or condition
-			AutoSetRestoreFlag<UCHAR> flags(&root_page.irt_rpt[id].irt_flags,
+			AutoSetRestoreFlag<USHORT> flags(&root_page->irt_rpt[id].irt_flags,
 				irt_expression | irt_condition, false);
 
-			BTR_description(vdr_tdbb, relation, &root_page, &idx, id);
+			BTR_description(vdr_tdbb, relation, root_page, &idx, id);
 		}
 
 		null_key = &nullKey;
@@ -3210,13 +3209,13 @@ Validation::RTN Validation::walk_root(jrd_rel* relation, bool getInfo)
 	if (!relPages->rel_index_root)
 		return corrupt(VAL_INDEX_ROOT_MISSING, relation);
 
-	index_root_page* page = 0;
+	index_root_page* page = nullptr;
 	WIN window(DB_PAGE_SPACE, -1);
 	fetch_page(!getInfo, relPages->rel_index_root, pag_root, &window, &page);
 
 	for (USHORT i = 0; i < page->irt_count; i++)
 	{
-		if (page->irt_rpt[i].getRoot() == 0)
+		if (!page->irt_rpt[i].getRoot())
 			continue;
 
 		MetaName index;
@@ -3242,7 +3241,7 @@ Validation::RTN Validation::walk_root(jrd_rel* relation, bool getInfo)
 			if (page->irt_rpt[i].irt_flags & irt_condition)
 			{
 				// No need to evaluate index expression
-				AutoSetRestoreFlag<UCHAR> flag(&page->irt_rpt[i].irt_flags, irt_expression, false);
+				AutoSetRestoreFlag<USHORT> flag(&page->irt_rpt[i].irt_flags, irt_expression, false);
 
 				IdxInfo info;
 				if (BTR_description(vdr_tdbb, relation, page, &info.m_desc, i))
@@ -3252,7 +3251,7 @@ Validation::RTN Validation::walk_root(jrd_rel* relation, bool getInfo)
 		}
 
 		output("Index %d (%s)\n", i + 1, index.c_str());
-		walk_index(relation, *page, i);
+		walk_index(relation, page, i);
 	}
 
 	release_page(&window);
diff --git a/src/jrd/validation.h b/src/jrd/validation.h
index 971e0617948..3a9e0e51ed3 100644
--- a/src/jrd/validation.h
+++ b/src/jrd/validation.h
@@ -213,7 +213,7 @@ class Validation
 	RTN walk_data_page(jrd_rel*, ULONG, ULONG, UCHAR&);
 	void walk_database();
 	void walk_generators();
-	RTN walk_index(jrd_rel*, Ods::index_root_page&, USHORT);
+	RTN walk_index(jrd_rel*, Ods::index_root_page*, USHORT);
 	void walk_pip();
 	RTN walk_pointer_page(jrd_rel*, ULONG);
 	RTN walk_record(jrd_rel*, const Ods::rhd*, USHORT, RecordNumber, bool);
diff --git a/src/utilities/gstat/dba.epp b/src/utilities/gstat/dba.epp
index 44c0ac4277e..33d73183df2 100644
--- a/src/utilities/gstat/dba.epp
+++ b/src/utilities/gstat/dba.epp
@@ -195,7 +195,7 @@ static void db_error(int);
 static USHORT get_format_length(ISC_STATUS*, isc_db_handle, isc_tr_handle, ISC_QUAD&);
 
 static dba_fil* db_open(const char*, USHORT);
-static const pag* db_read(SLONG page_number, bool ok_enc = false);
+static const pag* db_read(ULONG page_number, bool ok_enc = false);
 #ifdef WIN_NT
 static void db_close(void* file_desc);
 #else
@@ -264,7 +264,7 @@ public:
 	USHORT page_size;
 	USHORT dp_per_pp;
 	USHORT max_records;
-	SLONG page_number;
+	ULONG page_number;
 	pag* buffer1;
 	pag* buffer2;
 	pag* global_buffer;
@@ -619,7 +619,7 @@ int gstat(Firebird::UtilSvc* uSvc)
 	tddba->page_size = MAX(RAW_HEADER_SIZE, DIRECT_IO_BLOCK_SIZE);
 	tddba->global_buffer = (pag*) temp;
 	tddba->page_number = -1;
-	const header_page* header = (const header_page*) db_read((SLONG) 0);
+	const header_page* header = (const header_page*) db_read(HEADER_PAGE);
 
 	if (!Ods::isSupported(header))
 	{
@@ -1342,7 +1342,7 @@ static void analyze_data( dba_rel* relation, bool sw_record)
 
 	pointer_page* ptr_page = (pointer_page*) tddba->buffer1;
 
-	for (SLONG next_pp = relation->rel_pointer_page; next_pp; next_pp = ptr_page->ppg_next)
+	for (ULONG next_pp = relation->rel_pointer_page; next_pp; next_pp = ptr_page->ppg_next)
 	{
 		++relation->rel_pointer_pages;
 		memcpy(ptr_page, (const SCHAR*) db_read(next_pp), tddba->page_size);
@@ -1478,7 +1478,7 @@ static void analyze_blob(dba_rel* relation, const blh* blob, int length)
 	}
 	else
 	{
-		const int slots = (length - BLH_SIZE) / static_cast<int>(sizeof(SLONG));
+		const int slots = (length - BLH_SIZE) / static_cast<int>(sizeof(ULONG));
 		relation->rel_blob_pages += slots;
 		if (blob->blh_level == 1)
 		{
@@ -1488,13 +1488,13 @@ static void analyze_blob(dba_rel* relation, const blh* blob, int length)
 		{
 			relation->rel_blobs_level_2++;
 
-			SLONG pages[MAX_PAGE_SIZE / sizeof(SLONG)];
-			memcpy(pages, blob->blh_page, slots * sizeof(SLONG));
+			ULONG pages[MAX_PAGE_SIZE / sizeof(ULONG)];
+			memcpy(pages, blob->blh_page, slots * sizeof(ULONG));
 
 			for (int i = 0; i < slots; i++)
 			{
 				const blob_page* bpage = (const blob_page*) db_read(pages[i]);
-				relation->rel_blob_pages += bpage->blp_length / sizeof(SLONG);
+				relation->rel_blob_pages += bpage->blp_length / sizeof(ULONG);
 			}
 		}
 	}
@@ -1518,7 +1518,7 @@ static ULONG analyze_fragments(dba_rel* relation, const rhdf* header)
 
 	while (header->rhdf_flags & rhd_incomplete)
 	{
-		const SLONG f_page = header->rhdf_f_page;
+		const ULONG f_page = header->rhdf_f_page;
 		const USHORT f_line = header->rhdf_f_line;
 		const data_page* page = (const data_page*) db_read(f_page);
 		if (page->dpg_header.pag_type != pag_data || page->dpg_relation != relation->rel_id ||
@@ -1566,12 +1566,12 @@ static void analyze_index( const dba_rel* relation, dba_idx* index)
 
 	const index_root_page* index_root = (const index_root_page*) db_read(relation->rel_index_root);
 
-	SLONG page;
-	if (index_root->irt_count <= index->idx_id ||
-		!(page = index_root->irt_rpt[index->idx_id].getRoot()))
-	{
+	if (index_root->irt_count <= index->idx_id)
+		return;
+
+	ULONG page = index_root->irt_rpt[index->idx_id].getRoot();
+	if (!page)
 		return;
-	}
 
 	// CVC: The two const_cast's for bucket can go away if BTreeNode's functions
 	// are overloaded for constness. They don't modify bucket and pointer's contents.
@@ -1589,7 +1589,7 @@ static void analyze_index( const dba_rel* relation, dba_idx* index)
 	}
 
 	bool firstLeafNode = true;
-	SLONG number;
+	ULONG number;
 	FB_UINT64 duplicates = 0;
 
 	// Maximum key length is 1/4 of the used page-size
@@ -1712,7 +1712,7 @@ static ULONG analyze_versions( dba_rel* relation, const rhdf* header)
  **************************************/
 	//tdba* tddba = tdba::getSpecific();
 	ULONG space = 0, versions = 0;
-	SLONG b_page = header->rhdf_b_page;
+	ULONG b_page = header->rhdf_b_page;
 	USHORT b_line = header->rhdf_b_line;
 
 	while (b_page)
@@ -1923,7 +1923,7 @@ static dba_fil* db_open(const char* file_name, USHORT file_length)
 }
 
 
-static const pag* db_read( SLONG page_number, bool ok_enc)
+static const pag* db_read( ULONG page_number, bool ok_enc)
 {
 /**************************************
  *
@@ -1946,10 +1946,8 @@ static const pag* db_read( SLONG page_number, bool ok_enc)
 	tddba->page_number = page_number;
 
 	dba_fil* fil;
-	for (fil = tddba->files; page_number > (SLONG) fil->fil_max_page && fil->fil_next;)
-	{
+	for (fil = tddba->files; page_number > fil->fil_max_page && fil->fil_next;)
 		 fil = fil->fil_next;
-	}
 
 	page_number -= fil->fil_min_page - fil->fil_fudge;
 
@@ -2108,7 +2106,7 @@ static dba_fil* db_open(const char* file_name, USHORT file_length)
 }
 
 
-static const pag* db_read( SLONG page_number, bool ok_enc)
+static const pag* db_read( ULONG page_number, bool ok_enc)
 {
 /**************************************
  *
@@ -2128,10 +2126,8 @@ static const pag* db_read( SLONG page_number, bool ok_enc)
 	tddba->page_number = page_number;
 
 	dba_fil* fil;
-	for (fil = tddba->files; page_number > (SLONG) fil->fil_max_page && fil->fil_next;)
-	{
+	for (fil = tddba->files; page_number > fil->fil_max_page && fil->fil_next;)
 		fil = fil->fil_next;
-	}
 
 	page_number -= fil->fil_min_page - fil->fil_fudge;
 	const FB_UINT64 offset = ((FB_UINT64) page_number) * ((FB_UINT64) tddba->page_size);