2026-03-12 20:23:15

tpt/ash/disk_rereads.sql

@@ -0,0 +1,37 @@
+-- Copyright 2018 Tanel Poder. All rights reserved. More info at http://tanelpoder.com
+-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.
+
+-- experimental script - it will only capture a tiny portion of disk reread waits
+-- due to relatively infrequent sampling of ASH
+
+SELECT
+    SUM(rereads) 
+  , t.tablespace_name
+  , ts.block_size
+  , o.owner
+  , o.object_name
+FROM 
+    (SELECT current_obj#, p1, p2, TO_CHAR(p1)||':'||TO_CHAR(p2), COUNT(*) rereads 
+     FROM v$active_session_history 
+     WHERE 
+         sample_time < SYSDATE-1/24 
+     AND event = 'db file sequential read' 
+     GROUP BY 
+         current_obj#, p1, p2 
+     HAVING
+         COUNT(*) > 1
+    ) a
+  , dba_data_files t
+  , dba_tablespaces ts 
+  , dba_objects o
+WHERE 
+    a.p1 = t.file_id 
+AND t.tablespace_name = ts.tablespace_name 
+AND a.current_obj# = o.object_id (+)
+GROUP BY 
+    t.tablespace_name
+  , ts.block_size 
+  , o.owner
+  , o.object_name
+ORDER BY SUM(rereads) DESC
+/