Creating a physical standby database

Creating a physical standby database

A physical standby database is created from an existing other database. This other database will then be the primary database.

In this text, it is assumed that the primary database uses a spfile.

Getting the primary database ready

The primary database must meet two conditions before a standby database can be created from it:

• it must be in force logging mode and
• it must be in archive log mode (also automatic archiving must be enabled and a local archiving destination must be defined.

Use v$database.force_logging to determine if a database is in force logging mode. If not, enable it like so:

alter database force logging;

Use v$database.log_mode to determine if a database is in archive log mode. If not, enable it.

The (local) archive destination should be specified like so:

alter system set log_archive_dest_1='LOCATION=c:\oracle\oradb\arch MANDATORY' scope=both;

Creating the standby database

Copying the datafiles

The standby database is created from the existing datafiles of the primary database. These can be queried from the v$datafileview:

 select name from v$datafile;

These files must be copied to the standby database. However, the primary database must be shut down before they can be copied.

shutdown immediate;

After copying the datafiles, the primary database can be started up again.

startup

Creating a standby database control file

A control file needs to be created for the standby system. Execute the following on the primary system:

alter database create standby controlfile as '/some/path/to/a/file'

The created file must meet two conditions:

• Its filename must be different from any other control file
• Must be created after the backup of the datafiles.

Creating an init file

A pfile is created from the spfile. This pfile needs to be modified and then be used on the standby system to create an spfile from it.

create pfile='/some/path/to/a/file' from spfile

The following parameters must be modified or added:

• control_files
• standby_archive_dest
• db_file_name_convert (only if directory structure is different on primary and standby server)
• log_file_name_convert (only if directory structure is different on primary and standby server)
• log_archive_format
• log_archive_dest_1
  This value is used if a standby becomes primary during a switchover or a failover.
• standby_file_management
  Set to auto(??)
• remote_archive_enable
  Set it to true(??)
• instance_name
• lock_name_space (Only if standby and primary are on the same server. This makes no sense anyway)

Creating an oracle service (if on windows)

If the environment is running on windows, create a new oracle service on the standby system with oradim:

oradim -new -sid stdby -startmode manual

Configuring the listener

sqlnet.expire_time=2

In order to enable dead connection time, specify sqlnet.expire_time=2 (or any other appropriate value).

Creating net service names

net service names must be created on both the primary and standby database that will be used by log transport services. That is: something like to following lines must be added in thetnsnames.ora.

TO_STANDBY =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = stdby_host)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = stdby)
    )
  )

Creating the spfile on the standby database

On the still idle standby database, the pfile is turned into an spfile. Then the instance is started up.

set ORACLE_SID=stdby
sqlplus "/ as sysdba"

create spfile from pfile='/.../../modified-pfile';

Then, the standby database needs to be started as a physical standby database, however, without recovering:

startup nomount
alter database mount standby database;

Creating standby redo logs

On the standby database, standby redo logs can be created (if lgwr transmission is to be used).

alter database add standby logfile '/some/path/file_1.log' size 1M, '/some/path/file_2.log' size 1M, '/some/path/file_3.log' size 1M;

Archiving to the standby from the primary

alter system set log_archive_dest_2='service=to_standby lgwr' scope=both; 
alter system set log_archive_dest_state_2=enable scope=both;

Putting standby in recovery mode

alter database recover managed standby database disconnect from session;

Verify environment

After everything has been done, verify the physical standby database.  http://www.oracleops-support.com/2017/12/verify-standby-environment.html