Re: Physical Reads Direct on Standby

Hi All,

We've got a Standby database which has the apply lag suddenly started to peak at 10 minutes overnight during peak processing times, whereas previously it was near zero.   As usual everyone claims "nothing has changed" !

The only OEM tracked metric that seems to have changed is "Physical Read Direct" which is now bursting at the same times as we are getting the apply lags, whereas before it was negligible.   Redo rates at these times as the same as before and other CPU, Disk and Memory metrics seem pretty much the same.   The destination is SYNC AFIRM and the transport lag is pretty much zero.

Any suggestions on how to diagnose this?    I'm not really looking to fix it right now, just find out what has caused it to start happening (19.14).

Thanks for any tips!

Charlotte

Hi Charlotte,

Is this an active DG? If it is, then a full table scan may cause direct reads. If it isn't, it maybe caused by delayed block cleanout. If you have delayed block cleanout taking place on the primary side, it will have to be done on the standby as well. Can you please check whether you have the direct physical reads taking place on the primary, at the same time? If the standby is not open, than the standard techniques relying on AWR and ASH are not available. You may have to open a ticket with Oracle Support.

Regards

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