diff --git a/src/SQLInsight.Collectors/Concurrency/ActivityCollector.cs b/src/SQLInsight.Collectors/Concurrency/ActivityCollector.cs
index f2822b8..635b4d3 100644
--- a/src/SQLInsight.Collectors/Concurrency/ActivityCollector.cs
+++ b/src/SQLInsight.Collectors/Concurrency/ActivityCollector.cs
@@ -14,11 +14,12 @@ public sealed class ActivityCollector(int transactionMinutes = 10, int transacti
     private const string NotAgent = "s.is_user_process = 1 AND s.session_id <> @@SPID AND (s.program_name IS NULL OR s.program_name NOT LIKE N'SQLInsight Pro%')";
 
     /// <summary>
-    /// One row per open transaction of a user session. The statement is the running one, or else the session's last.
+    /// One row per open transaction of a user session, at most 100: those holding more log than the threshold first, then
+    /// the oldest. The statement is the running one (the first request of a MARS session), or else the session's last.
     /// Times are converted to UTC on the server.
     /// </summary>
     internal const string TransactionsSql = """
-        SELECT t.session_id, t.transaction_id, t.name, DATEADD(minute, DATEDIFF(minute, GETDATE(), GETUTCDATE()), t.begin_time),
+        SELECT TOP 100 t.session_id, t.transaction_id, t.name, DATEADD(minute, DATEDIFF(minute, GETDATE(), GETUTCDATE()), t.begin_time),
                t.used, t.reserved, t.db, t.dbs, s.login_name, s.host_name, s.program_name, s.status, r.wait_type,
                CAST(CASE WHEN r.sql_handle IS NOT NULL
                          THEN SUBSTRING(q.text, r.statement_start_offset / 2 + 1,
@@ -32,14 +33,16 @@ public sealed class ActivityCollector(int transactionMinutes = 10, int transacti
               LEFT JOIN sys.dm_tran_database_transactions dt ON dt.transaction_id = st.transaction_id AND dt.database_id <> 32767
               GROUP BY st.session_id, at.transaction_id) t
         JOIN sys.dm_exec_sessions s ON s.session_id = t.session_id
-        LEFT JOIN sys.dm_exec_requests r ON r.session_id = t.session_id
+        OUTER APPLY (SELECT TOP 1 x.sql_handle, x.statement_start_offset, x.statement_end_offset, x.wait_type FROM sys.dm_exec_requests x
+                     WHERE x.session_id = t.session_id ORDER BY x.request_id) r
         OUTER APPLY (SELECT TOP 1 c.most_recent_sql_handle FROM sys.dm_exec_connections c WHERE c.session_id = t.session_id) c
         OUTER APPLY sys.dm_exec_sql_text(COALESCE(r.sql_handle, c.most_recent_sql_handle)) q
         WHERE {notAgent} AND t.begin_time IS NOT NULL
+        ORDER BY CASE WHEN t.used + t.reserved >= {logBytes} THEN 0 ELSE 1 END, t.begin_time
         """;
 
     internal const string LongRequestsSql = """
-        SELECT r.session_id, DATEADD(minute, DATEDIFF(minute, GETDATE(), GETUTCDATE()), r.start_time), r.total_elapsed_time, r.command, r.status,
+        SELECT TOP 50 r.session_id, DATEADD(minute, DATEDIFF(minute, GETDATE(), GETUTCDATE()), r.start_time), r.total_elapsed_time, r.command, r.status,
                r.wait_type, r.wait_time, DB_NAME(r.database_id), s.login_name, s.host_name, s.program_name, r.blocking_session_id,
                CAST(SUBSTRING(q.text, r.statement_start_offset / 2 + 1,
                     CASE WHEN r.statement_end_offset = -1 THEN 1000 ELSE (r.statement_end_offset - r.statement_start_offset) / 2 + 1 END) AS nvarchar(1000))
@@ -47,6 +50,7 @@ public sealed class ActivityCollector(int transactionMinutes = 10, int transacti
         JOIN sys.dm_exec_sessions s ON s.session_id = r.session_id
         OUTER APPLY sys.dm_exec_sql_text(r.sql_handle) q
         WHERE {notAgent} AND r.total_elapsed_time > {thresholdMs} AND r.percent_complete = 0
+        ORDER BY r.total_elapsed_time DESC
         """;
 
     public override string Name => "activity";
@@ -56,7 +60,10 @@ public sealed class ActivityCollector(int transactionMinutes = 10, int transacti
     protected override async Task<ActivitySnapshot> CollectAsync(CollectorContext context, ActivitySnapshot? previous)
     {
         var ct = context.CancellationToken;
-        var transactions = await Db.QueryAsync(context.Connection, TransactionsSql.Replace("{notAgent}", NotAgent, StringComparison.Ordinal), r => new OpenTransaction(
+        var logBytes = (long)transactionLogMegabytes * 1024 * 1024;
+        var transactionsSql = TransactionsSql.Replace("{notAgent}", NotAgent, StringComparison.Ordinal)
+            .Replace("{logBytes}", logBytes.ToString(CultureInfo.InvariantCulture), StringComparison.Ordinal);
+        var transactions = await Db.QueryAsync(context.Connection, transactionsSql, r => new OpenTransaction(
             r.Int(0), r.Long(1), r.NullableString(2), Utc(r.DateTime(3)), r.Long(4), r.Long(5), r.NullableString(6), r.Int(7),
             r.NullableString(8), r.NullableString(9), r.NullableString(10), r.NullableString(11), r.NullableString(12), r.NullableString(13)), ct).ConfigureAwait(false);
         var thresholdMs = (long)requestMinutes * 60_000;
diff --git a/src/SQLInsight.Repository/InsightRepository.Activity.cs b/src/SQLInsight.Repository/InsightRepository.Activity.cs
index 505cf80..f3f381a 100644
--- a/src/SQLInsight.Repository/InsightRepository.Activity.cs
+++ b/src/SQLInsight.Repository/InsightRepository.Activity.cs
@@ -17,7 +17,8 @@ public sealed partial class InsightRepository
 {
     private static async Task SaveActivityAsync(SqlConnection connection, int instanceId, ActivitySnapshot snapshot)
     {
-        var kept = snapshot.Transactions.Where(t => ActivityAnalysis.IsWorthKeeping(t, snapshot.CapturedAt)).ToList();
+        // One row per transaction: a duplicate in the source would make the MERGE insert the same key twice.
+        var kept = snapshot.Transactions.Where(t => ActivityAnalysis.IsWorthKeeping(t, snapshot.CapturedAt)).DistinctBy(t => (t.SessionId, t.TransactionId)).ToList();
         if (kept.Count == 0)
         {
             return;