As all know most of the time this is due to because of primary DB archive destination 100% full and unable to archive a redo log.
Immediately we went and check, but surprisingly our primary archive destination is 95% free, and we had enough space. Unfortunately, Standby Database destination was 100% full.
We cleared the space on standby db server and Issue is resolved, everyone able to connect to DB now,
I can assume now that whoever reading this blog will thing that standby mode is “MAXIMUM PROTECTION MODE”, due to primary not able to transfer the redo because standby destination was full.
But that’s not the case, our standby mode is “Maximum Performance mode”, so technically it should not be the case.
Here is the Binding Variable comes into Play, we set to `mandatory` (default value:- optional). Why we set this to mandatory to make sure RMAN archive backup will delete archives from primary server only it applied on standy.
Since it set to mandatory, If the archiving operation of a mandatory destination fails, online redo log files cannot be overwritten, so Primary DB hung with error ORA-00257
So, lesson here is, Always double check dataguard broker property – Binding.