Thinking Out Loud

May 3, 2018

Multiplex Redo Log

Filed under: 12c,oracle — mdinh @ 4:14 am

When db_create_online_log_dest_1 is defined, REDO log is not multiplexed which is good for creating STANDBY REDO.

REDO log is created at db_create_online_log_dest_1 ONLY.

However, when creating ONLINE REDO, db_create_online_log_dest_1 should NOT be defined to be multiplexed.

REDO logs are created at db_create_file_dest and db_recovery_file_dest.

[oracle@db-asm-1 sql]$ sqlplus / as sysdba @ logfile.sql

SQL*Plus: Release 12.2.0.1.0 Production on Thu May 3 05:56:30 2018

Copyright (c) 1982, 2016, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

05:56:30 SYS @ owl:>show parameter db_create

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_create_file_dest                  string      +DATA
db_create_online_log_dest_1                      +FRA
db_create_online_log_dest_2
db_create_online_log_dest_3
db_create_online_log_dest_4
db_create_online_log_dest_5
05:56:30 SYS @ owl:>show parameter db_recovery_file

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      +FRA
db_recovery_file_dest_size           big integer 7116M

05:56:30 SYS @ owl:>select group#,member,type,status from v$logfile order by 1,2 asc;

    GROUP# MEMBER                                                                           TYPE    STATUS
---------- -------------------------------------------------------------------------------- ------- -------
         1 +DATA/OWL/ONLINELOG/group_1.261.962643743                                        ONLINE
         1 +FRA/OWL/ONLINELOG/group_1.257.962643743
         2 +DATA/OWL/ONLINELOG/group_2.262.962643743
         2 +FRA/OWL/ONLINELOG/group_2.258.962643743
         3 +DATA/OWL/ONLINELOG/group_3.263.962643745
         3 +FRA/OWL/ONLINELOG/group_3.259.962643745

6 rows selected.

05:56:30 SYS @ owl:>select group#,thread#,sequence#,bytes,status from v$log order by 1,2;

    GROUP#    THREAD#  SEQUENCE#      BYTES STATUS
---------- ---------- ---------- ---------- ----------------
         1          1         79  104857600 CURRENT
         2          1         77  104857600 INACTIVE
         3          1         78  104857600 INACTIVE

05:56:30 SYS @ owl:>select group#,thread#,sequence#,bytes,status from v$standby_log order by 1,2;

no rows selected

05:56:30 SYS @ owl:>alter database add standby logfile thread 1 group 11 size 104857600;

Database altered.

05:57:03 SYS @ owl:>alter system set db_create_online_log_dest_1='';

System altered.

05:57:39 SYS @ owl:>alter database add logfile thread 1 group 4 size 104857600;

Database altered.

05:58:01 SYS @ owl:>@logfile.sql
05:58:06 SYS @ owl:>set lines 200 tab off trimsp on pages 1000
05:58:06 SYS @ owl:>col member for a80
05:58:06 SYS @ owl:>break on TYPE
05:58:06 SYS @ owl:>set echo on
05:58:06 SYS @ owl:>show parameter db_create

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_create_file_dest                  string      +DATA
db_create_online_log_dest_1
db_create_online_log_dest_2
db_create_online_log_dest_3
db_create_online_log_dest_4
db_create_online_log_dest_5
05:58:06 SYS @ owl:>show parameter db_recovery_file

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      +FRA
db_recovery_file_dest_size           big integer 7116M
05:58:06 SYS @ owl:>select group#,member,type,status from v$logfile order by 1,2 asc;

    GROUP# MEMBER                                                                           TYPE    STATUS
---------- -------------------------------------------------------------------------------- ------- -------
         1 +DATA/OWL/ONLINELOG/group_1.261.962643743                                        ONLINE
         1 +FRA/OWL/ONLINELOG/group_1.257.962643743
         2 +DATA/OWL/ONLINELOG/group_2.262.962643743
         2 +FRA/OWL/ONLINELOG/group_2.258.962643743
         3 +DATA/OWL/ONLINELOG/group_3.263.962643745
         3 +FRA/OWL/ONLINELOG/group_3.259.962643745
         4 +DATA/OWL/ONLINELOG/group_4.267.975131881
         4 +FRA/OWL/ONLINELOG/group_4.295.975131881
        11 +FRA/OWL/ONLINELOG/group_11.296.975131823                                        STANDBY

9 rows selected.

05:58:07 SYS @ owl:>select group#,thread#,sequence#,bytes,status from v$log order by 1,2;

    GROUP#    THREAD#  SEQUENCE#      BYTES STATUS
---------- ---------- ---------- ---------- ----------------
         1          1         79  104857600 CURRENT
         2          1         77  104857600 INACTIVE
         3          1         78  104857600 INACTIVE
         4          1          0  104857600 UNUSED

05:58:07 SYS @ owl:>select group#,thread#,sequence#,bytes,status from v$standby_log order by 1,2;

    GROUP#    THREAD#  SEQUENCE#      BYTES STATUS
---------- ---------- ---------- ---------- ----------
        11          1          0  104857600 UNASSIGNED

05:58:07 SYS @ owl:>
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