Local time: Mon 2020-07-06 22:22:40 +08

  Universal time: Mon 2020-07-06 14:22:40 UTC

        RTC time: Mon 2020-07-06 14:22:40

       Time zone: Asia/Singapore (+08, +0800)

     NTP enabled: yes

NTP synchronized: yes

 RTC in local TZ: no

      DST active: n/a

The output above shows that the system’s time zone is set to Singapore.

The system time zone is configured by a link i.e. /etc/localtime file to a binary time zone’s identifier in the /usr/share/zoneinfo directory.

$ ls -l /etc/localtime

lrwxrwxrwx 1 root root 36 Jul  6 22:03 /etc/localtime -> ../usr/share/zoneinfo/Asia/Singapore

Make sure to identify the exact time zone which needs to be set in Region/City format.

To view all available time zones, use the timedatectl command or list the files in the /usr/share/zoneinfo directory:

# timedatectl list-timezones

America/Montserrat

America/Nassau

America/New_York

America/Nipigon

America/Nome

America/Noronha

sudo timedatectl set-timezone America/New_York

or  doing in UTC then

sudo timedatectl set-timezone UTC

To verify the change, invoke the timedatectl command again:

timedatectl

                    Local time: Mon 2020-07-06 14:28:53 UTC

  Universal time: Mon 2020-07-06 14:28:53 UTC

        RTC time: Mon 2020-07-06 14:28:53

       Time zone: UTC (UTC, +0000)

     NTP enabled: no

NTP synchronized: yes

 RTC in local TZ: yes

      DST active: n/a

--------------------------------------------------------------------------

We can also change Time Zone by Creating a Symlink(Especially used in old system)

If you are running an older Linux distribution and the timedatectl utility is not present on your system, you can change the timezone by symlinking /etc/localtime to the time zone in the /usr/share/zoneinfo directory.

Remove the current symlink or file:

sudo rm -rf /etc/localtime or  sudo unlink /etc/localtime 

Identify the timezone you want to configure and create a symlink:

sudo ln -s /usr/share/zoneinfo/UTC /etc/localtime

Verify the /etc/localtime file 

 ls -l /etc/localtime

lrwxrwxrwx. 1 root root 25 Jul  6  2020 /etc/localtime -> ../usr/share/zoneinfo/UTC

After upgrading EBS database to 11GR2, we can encounter error while running autoconfig on the DB node 

java.lang.UnsatisfiedLinkError: /d11/oracle/TEST/db/tech_st/11.2.0/lib/libnjni11.so: /d11/oracle/TEST/db/11.2.0/lib/libnjni11.so: wrong ELF class: ELFCLASS64 (Possible cause: architecture word width mismatch)

To fix this issue, Edit the database node xml as below and re-run the autoconfig.

 <JDK_TOP oa_var="s_jdktop">/d11/oracle/TEST/db/tech_st/11.2.0/appsutil/jre</JDK_TOP>

 <JRE_TOP oa_var="s_jretop">/d11/oracle/TEST/db/tech_st/11.2.0/appsutil/jre</JRE_TOP>

update to 

 <JDK_TOP oa_var="s_jdktop">/d11/oracle/TEST/db/tech_st/11.2.0/jdk/jre</JDK_TOP>

 <JRE_TOP oa_var="s_jretop">/d11/oracle/TEST/db/tech_st/11.2.0/jdk/jre</JRE_TOP>

----

From 11gR2 DB version onwards AutoConfig on DB node uses the JRE from <Oracle_Home>/jdk/jre where as earlier versions of DB uses JRE from $ORACLE_HOME/appsutil/jre

The Flashback Database feature provides a way to quickly revert entire Oracle database to the state it was in at a past point in time.

To use the Flashback database feature the database must be running in archivelog mode.

Enable flashback feature in the database when it was running in the source release.

Set the environment variables to point to the source Oracle Home (10.2.0.4) and perform a 'startup mount'

SQL> startup mount

ORACLE instance started.

Total System Global Area  918552576 bytes

Fixed Size                  2025072 bytes

Variable Size             239077776 bytes

Database Buffers          675282944 bytes

Redo Buffers                2166784 bytes

Database mounted.

Turn on flashback

SQL> alter database flashback on;

Database altered

Create guaranteed restore point

SQL> CREATE RESTORE POINT before_upgrade GUARANTEE FLASHBACK DATABASE;

Restore point created.

Run the following query to view all guaranteed restore points created.

SQL> SELECT NAME, SCN, TIME, DATABASE_INCARNATION# DI,GUARANTEE_FLASHBACK_DATABASE,

     STORAGE_SIZE FROM V$RESTORE_POINT WHERE GUARANTEE_FLASHBACK_DATABASE='YES';

NAME             SCN     TIME                 DI         GUA     STORAGE_SIZE

----------       --- ------------       -------------    ---    ------------

BEFORE_UPGRADE  34552155 23-JUN-20  10.58.42.000000000 AM  YES    312672256

Query the dba_registry view to see the component status and version before upgrade

SQL> select comp_name, status, version from dba_registry;

COMP_NAME

--------------------------------------------------------------------------------

STATUS      VERSION

----------- ------------------------------

Oracle Database Catalog Views

VALID       10.2.0.4.0

Oracle Database Packages and Types

VALID       10.2.0.4.0

Shutdown the database

SQL> shutdown immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

 

Set the environment variables to point to the target Oracle Home (11.2.0.4) to which the database will be upgraded to.

compatible-10.2.0.4

Please note that changing COMPATIBLE initialization parameter at this stage will prevent use of the downgrade procedure or the ability to flash back the database to a point prior to this.

Startup the database in upgrade mode using the 11.2.0.4 Oracle Home

SQL> startup upgrade (using 11.2.0.4 Oracle Home)

ORACLE instance started.

Total System Global Area  918552576 bytes

Fixed Size                  2077008 bytes

Variable Size             234884784 bytes

Database Buffers          675282944 bytes

Redo Buffers                6307840 bytes

Database mounted.

Database opened.

Run the upgrade script (catupgrd.sql)

SQL> @?/rdbms/admin/catupgrd.sql

Validate any invalid objects after upgrade if any

SQL> @?/rdbms/admin/utlrp.sql

Query the dba_registry view to see the component status and version after upgrade

SQL> select comp_name, version, status from dba_registry;

COMP_NAME

--------------------------------------------------------------------------------

VERSION STATUS

------------------------------ -----------

Oracle Database Catalog Views

11.2.0.4.0 VALID

Oracle Database Packages and Types

11.2.0.4.0 VALID

 

Note that data from any transactions that occur after the point in time to which the database is recovered are lost. Flashback Database is an excellent tool for backing out the database upgrade, Using Flashback Database with sufficient space and creating a guaranteed restore point immediately prior to the upgrade is the fastest method to fallback as compared to a restore operation or a database downgrade.

Using flashback database rather than the conventional downgrade procedure is far quicker. This is only practical when only the database upgrade has been done and no application data changes have occurred.

The steps for flashing back the database after upgrade or after a failed upgrade are

Set the environment variables to the 11.2.0.4 Oracle Home

Shut down the upgraded database

SQL> shutdown immediate

Startup mount the 11.2.0.4 database using the 11.2.0.4 Oracle Home and flashback the database to the guaranteed restore point which was created prior to the upgrade.

SQL> startup mount

SQL> flashback database to restore point before_upgrade;

SQL> shutdown immediate

Set the environment variable to point to the old Oracle Home (10.2.0.4)

SQL> startup mount

SQL> alter database open resetlogs;

query the dba_registry view to see the database component status and version

SQL> select comp_name, version, status from dba_registry;

COMP_NAME

--------------------------------------------------------------------------------

VERSION STATUS

------------------------------ -----------

Oracle Database Catalog Views

10.2.0.4.0 VALID

Oracle Database Packages and Types

10.2.0.4.0 VALID