Re: How to figure out which statements are locking row in one table?

  • From: Tim Gorman <tim.evdbt@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Wed, 16 Jun 2021 17:44:48 -0700

Depending on how long you're retaining AWR data, you might even be able to figure out when it started happening by running similar queries on DBA_HIST_ACTIVE_SESS_HISTORY?

Years back, I used to do a presentation at conferences called "Database Forensics" about using the ASH views this way.



On 6/16/2021 5:41 PM, Tim Gorman wrote:

Perhaps...

select SQL_ID, count(*) from V$ACTIVE_SESSION_HISTORY where EVENT = 'enq: TX - row lock wait' group by SQL_ID order by 2 desc;

...or...

select SQL_ID, count(*) from V$ACTIVE_SESSION_HISTORY where CURRENT_OBJ# = 93432 group by SQL_ID order by 2 desc;

...to find what's locking on the MESSAGE table PART_3 partition, for example?



On 6/16/2021 5:29 PM, Mladen Gogala wrote:

I have a problem: my application is doing a lot of locking. I got the segments that are being locked from an AWR report:


      Segments by Row Lock Waits

  * % of Capture shows % of row lock waits for each top segment compared
  * with total row lock waits for all segments captured by the Snapshot
  * When ** MISSING ** occurs, some of the object attributes may not
    be available

Owner Tablespace Name Object Name Subobject Name Obj. Type Obj# Dataobj# Row Lock Waits % of Capture PDB Name
APP_USER USERS MESSAGE PART_3 TABLE PARTITION 93432 93432 852,300 97.56 USACH
APP_USER USERS CLEARINGRECNCLNTOTAL TABLE 100137 100137 17,403 1.99 USACH
APP_USER USERS PAYMENTSFEEDCHUNK TABLE 100186 100186 2,813 0.32 USACH
APP_USER USERS FEDACCOUNTBALANCES TABLE 99552 99552 971 0.11 USACH
APP_USER USERS CLEARINGSYSTEMACCOUNT TABLE 99718 99718 111 0.01 USACH

------------------------------------------------------------------------

How do I determine the SQL statements that are doing all the locking?  I even considered locking the table in the exclusive mode and then finding the sessions waiting for the lock.. Obviously almost all the row lock waits are concentrated in a single partition. A part of the application needs to be rewritten but I need to figure out which part.  Any ideas how to get the SQL statement(s) doing the locking?

--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com
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