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  • 15. Re: Standby SCN greater than SCN on Primary
    mseberg Guru
    Currently Being Moderated
    Hello again;

    Sorry for the delay. I don't understand either. Feels like a bug but I hate to guess.

    Would consider an SR and would monitor close for a few days.

    I have asked CKPT to review and he may have an additional insight.

    Very interesting.

    Best Regards

    mseberg
  • 16. Re: Standby SCN greater than SCN on Primary
    CKPT Guru
    Currently Being Moderated
    Hello,

    This situation is really interesting. Usually the primary SCN will be ahead than standby database. and CURRENT_SCN from standby refers to the SCN of redo application.
    Moreover i would like to see the CHECKPOINT_CHANGE# of datafiles from primary and standby, Does this output also vary?

    and try to stop the MRP and then see the CURRENT_SCN from v$database of both primary and standby.
    As Mseberg said if this is the case, Better to check with Oracle Support by submitting SR.

    Thank you.
  • 17. Re: Standby SCN greater than SCN on Primary
    978280 Newbie
    Currently Being Moderated
    Hi CKPT,

    The SCN on the standby seems to be less than the Primary. As said yesterday, I am not sure how it turned to be low. Here is the outcome of what you asked.

    Prirmary:
    SQL> select current_scn from v$database;
    
    CURRENT_SCN
    -----------
      422793745
    
    SQL> select file#,checkpoint_change# from v$datafile;
    
         FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
             1          422776760
             2          422776760
             3          422776760
             4          422776760
             5          422776760
             6          422776760
             7          422776760
             8          422776760
             9          422776760
            10          422776760
            11          422776760
    
         FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
            12          422776760
            13          422776760
            14          422776760
            15          422776760
            16          422776760
            17          422776760
    Standby:
    SQL> select current_scn from v$database;
    
    CURRENT_SCN
    -----------
      422793741
    
    SQL> select file#,checkpoint_change# from v$datafile;
    
         FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
             1          422776760
             2          422776760
             3          422776760
             4          422776760
             5          422776760
             6          422776760
             7          422776760
             8          422776760
             9          422776760
            10          422776760
            11          422776760
    
         FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
            12          422776760
            13          422776760
            14          422776760
            15          422776760
            16          422776760
            17          422776760
    I have another set of Primary and standby database with same 11.2.0.3 version and even here I am facing the same issue. Here is the details:

    Primary:
    SQL> select status,instance_name,database_role from v$database,v$instance;
    
    STATUS       INSTANCE_NAME    DATABASE_ROLE
    ------------ ---------------- ----------------
    OPEN         MRAT            PRIMARY
    
    SQL>
    SQL> col current_scn for 999999999999999999
    SQL> select current_scn from v$database;
    
            CURRENT_SCN
    -------------------
            705523588
    Standby:
    SQL> select status,instance_name,database_role from v$database,v$instance;
    
    STATUS       INSTANCE_NAME    DATABASE_ROLE
    ------------ ---------------- ----------------
    OPEN         MRAS            PHYSICAL STANDBY
    
    SQL> col current_scn for 999999999999999999
    SQL> select current_scn from v$database;
    
            CURRENT_SCN
    -------------------
            705523669
    Here the SCN on standby seems to be higher than primary. This also uses the Real Time apply and the standby is in sync with the primary. Below is the checkpoint_change# for the 2nd set of database and the chekcpoint_change# shows less on the standby than primary.

    Primary:
     FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
             1        705517464
             2        705517464
             3        705517464
             4        705517464
             5        705517464
             6        705517464
            11        705517464
            13        705517464
            14        705517464
            15        705517464
            16        705517464
    
         FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
            17        705517464
            18        705517464
            19        705517464
            20        705517464
            21        705517464
            22        705517464
            23        705517464
            24        705517464
            25        705517464
            26        705517464
            27        705517464
    Standby:
    FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
             1        705503643
             2        705503643
             3        705503643
             4        705503643
             5        705503643
             6        705503643
            11        705503643
            13        705503643
            14        705503643
            15        705503643
            16        705503643
    
         FILE# CHECKPOINT_CHANGE#
    ---------- ------------------
            17        705503643
            18        705503643
            19        705503643
            20        705503643
            21        705503643
            22        705503643
            23        705503643
            24        705503643
            25        705503643
            26        705503643
            27        705503643
  • 18. Re: Standby SCN greater than SCN on Primary
    CKPT Guru
    Currently Being Moderated
    I have one last question. CURRENT_SCN is like clock which is never stops until instance is closed. Which is never going to stop even though there is no activity on database.

    Just a stone, what is the time you taking to query between primary and standby? Probably you querying first on Primary and after some time like 20-30 seconds you querying on standby?
    Can you try with couple of tests by querying immediately in standby and then primary and vice versa?

    and if still the issue is same, then i suggest to submit SR to oracle support.
    Thanks.
  • 19. Re: Standby SCN greater than SCN on Primary
    978280 Newbie
    Currently Being Moderated
    Thanks CKPT. I have opened two sessions, one in primary and the other for a standby. I am running the CURRENT_SCN on both the databases at the same time.
    I guess the difference in time the query is run may be 1 second.

    I'll certainly check for a few more duration and if its the same, then I'll raise an SR.
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