diff --git a/runtime/src/accounts_db.rs b/runtime/src/accounts_db.rs
index df0bbe3424..2031b56960 100644
--- a/runtime/src/accounts_db.rs
+++ b/runtime/src/accounts_db.rs
@@ -5512,7 +5512,7 @@ impl AccountsDb {
             };
             timings.calc_storage_size_quartiles(&combined_maps);
 
-            self.calculate_accounts_hash_without_index(
+            let result = self.calculate_accounts_hash_without_index(
                 &CalcAccountsHashConfig {
                     storages: &storages,
                     use_bg_thread_pool: !is_startup,
@@ -5520,7 +5520,11 @@ impl AccountsDb {
                     ancestors: can_cached_slot_be_unflushed.then(|| ancestors),
                 },
                 timings,
-            )
+            );
+            // now that calculate_accounts_hash_without_index is complete, we can remove old roots
+            self.remove_old_roots(slot);
+
+            result
         } else {
             self.calculate_accounts_hash(
                 slot,
@@ -5787,6 +5791,18 @@ impl AccountsDb {
         }
     }
 
+    /// get rid of old original_roots
+    fn remove_old_roots(&self, slot: Slot) {
+        // epoch_schedule::DEFAULT_SLOTS_PER_EPOCH is a sufficient approximation for now
+        let width = solana_sdk::epoch_schedule::DEFAULT_SLOTS_PER_EPOCH * 11 / 10; // a buffer
+        if slot > width {
+            let min_root = slot - width;
+            let valid_slots = HashSet::default();
+            self.accounts_index
+                .remove_old_original_roots(min_root, &valid_slots);
+        }
+    }
+
     /// Only called from startup or test code.
     pub fn verify_bank_hash_and_lamports(
         &self,
diff --git a/runtime/src/accounts_index.rs b/runtime/src/accounts_index.rs
index d98593bdbf..ccc095898b 100644
--- a/runtime/src/accounts_index.rs
+++ b/runtime/src/accounts_index.rs
@@ -400,7 +400,12 @@ impl<T: IndexValue> PreAllocatedAccountMapEntry<T> {
 
 #[derive(Debug)]
 pub struct RootsTracker {
+    /// current set of roots active in approx. the current epoch
     pub(crate) roots: RollingBitField,
+    /// Set of roots approx. within the current epoch that are roots now or were roots at one point in time.
+    /// A root could remain here if all entries in the append vec at that root are cleaned/shrunk and there are no
+    ///  more entries that slot. 'roots' will no longer contain such roots.
+    pub(crate) roots_original: RollingBitField,
     uncleaned_roots: HashSet<Slot>,
     previous_uncleaned_roots: HashSet<Slot>,
 }
@@ -418,6 +423,7 @@ impl RootsTracker {
     pub fn new(max_width: u64) -> Self {
         Self {
             roots: RollingBitField::new(max_width),
+            roots_original: RollingBitField::new(max_width),
             uncleaned_roots: HashSet::new(),
             previous_uncleaned_roots: HashSet::new(),
         }
@@ -1682,7 +1688,9 @@ impl<T: IndexValue> AccountsIndex<T> {
         let mut w_roots_tracker = self.roots_tracker.write().unwrap();
         // `AccountsDb::flush_accounts_cache()` relies on roots being added in order
         assert!(slot >= w_roots_tracker.roots.max_inclusive());
+        // 'slot' is a root, so it is both 'root' and 'original'
         w_roots_tracker.roots.insert(slot);
+        w_roots_tracker.roots_original.insert(slot);
         // we delay cleaning until flushing!
         if !caching_enabled {
             w_roots_tracker.uncleaned_roots.insert(slot);
@@ -1701,6 +1709,51 @@ impl<T: IndexValue> AccountsIndex<T> {
         self.roots_tracker.read().unwrap().roots.max_inclusive()
     }
 
+    /// return the lowest original root >= slot, including roots_original and ancestors
+    pub fn get_next_original_root(
+        &self,
+        slot: Slot,
+        ancestors: Option<&Ancestors>,
+    ) -> Option<Slot> {
+        {
+            let roots_tracker = self.roots_tracker.read().unwrap();
+            for root in slot..roots_tracker.roots_original.max_exclusive() {
+                if roots_tracker.roots_original.contains(&root) {
+                    return Some(root);
+                }
+            }
+        }
+        // ancestors are higher than roots, so look for roots first
+        if let Some(ancestors) = ancestors {
+            let min = std::cmp::max(slot, ancestors.min_slot());
+            for root in min..=ancestors.max_slot() {
+                if ancestors.contains_key(&root) {
+                    return Some(root);
+                }
+            }
+        }
+        None
+    }
+
+    /// roots are inserted into 'roots_original' and 'roots' as a new root is made.
+    /// roots are removed form 'roots' as all entries in the append vec become outdated.
+    /// This function exists to clean older entries from 'roots_original'.
+    /// all roots < 'oldest_slot_to_keep' are removed from 'roots_original'.
+    pub fn remove_old_original_roots(&self, oldest_slot_to_keep: Slot, keep: &HashSet<Slot>) {
+        let w_roots_tracker = self.roots_tracker.read().unwrap();
+        let mut roots = w_roots_tracker
+            .roots_original
+            .get_all_less_than(oldest_slot_to_keep);
+        roots.retain(|root| !keep.contains(root));
+        drop(w_roots_tracker);
+        if !roots.is_empty() {
+            let mut w_roots_tracker = self.roots_tracker.write().unwrap();
+            roots.into_iter().for_each(|root| {
+                w_roots_tracker.roots_original.remove(&root);
+            });
+        }
+    }
+
     /// Remove the slot when the storage for the slot is freed
     /// Accounts no longer reference this slot.
     /// return true if slot was a root
@@ -1935,6 +1988,134 @@ pub mod tests {
         }
     }
 
+    #[test]
+    fn test_get_next_original_root() {
+        let ancestors = None;
+        let index = AccountsIndex::<bool>::default_for_tests();
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), None);
+        }
+        // roots are now [1]. 0 and 1 both return 1
+        index.add_root(1, true);
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(1));
+        }
+        assert_eq!(index.get_next_original_root(2, ancestors), None); // no roots after 1, so asking for root >= 2 is None
+
+        // roots are now [1, 3]. 0 and 1 both return 1. 2 and 3 both return 3
+        index.add_root(3, true);
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(1));
+        }
+        for slot in 2..4 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(3));
+        }
+        assert_eq!(index.get_next_original_root(4, ancestors), None); // no roots after 3, so asking for root >= 4 is None
+    }
+
+    #[test]
+    fn test_get_next_original_root_ancestors() {
+        let orig_ancestors = Ancestors::default();
+        let ancestors = Some(&orig_ancestors);
+        let index = AccountsIndex::<bool>::default_for_tests();
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), None);
+        }
+        // ancestors are now [1]. 0 and 1 both return 1
+        let orig_ancestors = Ancestors::from(vec![1]);
+        let ancestors = Some(&orig_ancestors);
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(1));
+        }
+        assert_eq!(index.get_next_original_root(2, ancestors), None); // no roots after 1, so asking for root >= 2 is None
+
+        // ancestors are now [1, 3]. 0 and 1 both return 1. 2 and 3 both return 3
+        let orig_ancestors = Ancestors::from(vec![1, 3]);
+        let ancestors = Some(&orig_ancestors);
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(1));
+        }
+        for slot in 2..4 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(3));
+        }
+        assert_eq!(index.get_next_original_root(4, ancestors), None); // no roots after 3, so asking for root >= 4 is None
+    }
+
+    #[test]
+    fn test_get_next_original_root_roots_and_ancestors() {
+        let orig_ancestors = Ancestors::default();
+        let ancestors = Some(&orig_ancestors);
+        let index = AccountsIndex::<bool>::default_for_tests();
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), None);
+        }
+        // roots are now [1]. 0 and 1 both return 1
+        index.add_root(1, true);
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(1));
+        }
+        assert_eq!(index.get_next_original_root(2, ancestors), None); // no roots after 1, so asking for root >= 2 is None
+
+        // roots are now [1] and ancestors are now [3]. 0 and 1 both return 1. 2 and 3 both return 3
+        let orig_ancestors = Ancestors::from(vec![3]);
+        let ancestors = Some(&orig_ancestors);
+        for slot in 0..2 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(1));
+        }
+        for slot in 2..4 {
+            assert_eq!(index.get_next_original_root(slot, ancestors), Some(3));
+        }
+        assert_eq!(index.get_next_original_root(4, ancestors), None); // no roots after 3, so asking for root >= 4 is None
+    }
+
+    #[test]
+    fn test_remove_old_original_roots() {
+        let index = AccountsIndex::<bool>::default_for_tests();
+        index.add_root(1, true);
+        index.add_root(2, true);
+        assert_eq!(
+            index.roots_tracker.read().unwrap().roots_original.get_all(),
+            vec![1, 2]
+        );
+        let empty_hash_set = HashSet::default();
+        index.remove_old_original_roots(2, &empty_hash_set);
+        assert_eq!(
+            index.roots_tracker.read().unwrap().roots_original.get_all(),
+            vec![2]
+        );
+        index.remove_old_original_roots(3, &empty_hash_set);
+        assert!(
+            index
+                .roots_tracker
+                .read()
+                .unwrap()
+                .roots_original
+                .is_empty(),
+            "{:?}",
+            index.roots_tracker.read().unwrap().roots_original.get_all()
+        );
+
+        // now use 'keep'
+        let index = AccountsIndex::<bool>::default_for_tests();
+        index.add_root(1, true);
+        index.add_root(2, true);
+        let hash_set_1 = vec![1].into_iter().collect();
+        assert_eq!(
+            index.roots_tracker.read().unwrap().roots_original.get_all(),
+            vec![1, 2]
+        );
+        index.remove_old_original_roots(2, &hash_set_1);
+        assert_eq!(
+            index.roots_tracker.read().unwrap().roots_original.get_all(),
+            vec![1, 2]
+        );
+        index.remove_old_original_roots(3, &hash_set_1);
+        assert_eq!(
+            index.roots_tracker.read().unwrap().roots_original.get_all(),
+            vec![1]
+        );
+    }
+
     const COLLECT_ALL_UNSORTED_FALSE: bool = false;
 
     #[test]
diff --git a/runtime/src/ancestors.rs b/runtime/src/ancestors.rs
index 844fc99a50..42730efd98 100644
--- a/runtime/src/ancestors.rs
+++ b/runtime/src/ancestors.rs
@@ -85,6 +85,10 @@ impl Ancestors {
         self.len() == 0
     }
 
+    pub fn min_slot(&self) -> Slot {
+        self.ancestors.min().unwrap_or_default()
+    }
+
     pub fn max_slot(&self) -> Slot {
         self.ancestors.max_exclusive().saturating_sub(1)
     }
diff --git a/runtime/src/rolling_bit_field.rs b/runtime/src/rolling_bit_field.rs
index 0c86237e4e..8fdf4862b4 100644
--- a/runtime/src/rolling_bit_field.rs
+++ b/runtime/src/rolling_bit_field.rs
@@ -240,7 +240,6 @@ impl RollingBitField {
     }
 
     /// return all items < 'max_slot_exclusive'
-    #[allow(dead_code)] // temporary
     pub fn get_all_less_than(&self, max_slot_exclusive: Slot) -> Vec<u64> {
         let mut all = Vec::with_capacity(self.count);
         self.excess.iter().for_each(|slot| {