Overview of Oracle time zone files - Amazon Relational Database Service
How the time zone file affects data transferAutomatic updates using the TIMEZONE_FILE_AUTOUPGRADE option

Overview of Oracle time zone files

An Oracle Database time zone file stores the following information:

  • Offset from Coordinated Universal Time (UTC)

  • Transition times for Daylight Saving Time (DST)

  • Abbreviations for standard time and DST

Oracle Database supplies multiple versions of time zone files. When you create an Oracle database in an on-premises environment, you choose the time zone file version. For more information , see Choosing a Time Zone File in the Oracle Database Globalization Support Guide.

If the rules change for DST, Oracle publishes new time zone files. Oracle releases these new time zone files independently of the schedule for quarterly Release Updates (RUs) and Release Update Revisions (RURs). The time zone files reside on the database host in the directory $ORACLE_HOME/oracore/zoneinfo/. The time zone file names use the format DSTvversion, as in DSTv35.

How the time zone file affects data transfer

In Oracle Database, the TIMESTAMP WITH TIME ZONE data type stores time stamp and time zone data. Data with the TIMESTAMP WITH TIME ZONE data type uses the rules in the associated time zone file version. Thus, existing TIMESTAMP WITH TIME ZONE data is affected when you update the time zone file.

Problems can occur when you transfer data between databases that use different versions of the time zone file. For example, if you import data from a source database with a higher time zone file version than the target database, the database issues the ORA-39405 error. Previously, you had to work around this error by using either of the following techniques:

  • Create an RDS for Oracle DB instance with the desired time zone file, export data from your source database, and then import it into the new database.

  • Use AWS DMS or logical replication to migrate your data.

Automatic updates using the TIMEZONE_FILE_AUTOUPGRADE option

When the option group attached to your RDS for Oracle DB instance includes the TIMEZONE_FILE_AUTOUPGRADE option, RDS updates your time zone files automatically. By ensuring that your Oracle databases use the same time zone file version, you avoid time-consuming manual techniques when you move data between different environments. The TIMEZONE_FILE_AUTOUPGRADE option is supported for both container databases (CDBs) and non-CDBs.

When you add the TIMEZONE_FILE_AUTOUPGRADE option to your option group, you can choose whether to add the option immediately or during the maintenance window. After your DB instance applies the new option, RDS checks whether it can install a newer DSTvversion file. The target DSTvversion depends on the following:

  • The minor engine version that your DB instance is currently running

  • The minor engine version to which you want to upgrade your DB instance

For example, your current time zone file version might be DSTv33. When RDS applies the update to your option group, it might determine that DSTv34 is currently available on your DB instance file system. RDS will then update your time zone file to DSTv34 automatically.

To find the available DST versions in the supported RDS release updates, look at the patches in Release notes for Amazon Relational Database Service (Amazon RDS) for Oracle. For example, version 19.0.0.0.ru-2022-10.rur-2022-10.r1 lists patch 34533061: RDBMS - DSTV39 UPDATE - TZDATA2022C.