Plan the Oracle Database Migration

To plan the Oracle Database migration, you must inventory the source environment and decide on the best migration strategy.

Inventory the Source Environment

Inventorying the environment includes tasks such as ensuring that you have the supported Oracle Database versions and configurations.

Ensure that you have the supported versions and configurations.

At a minimum, you should have at least Oracle Database 11g 11.2.0.4 (standalone) or Oracle Database 12c release 1 (12.1.0.2) (standalone).
Determine the size of the database files of the source database.

You can find the total size of the database files of the database that you plan to migrate, including redo log files sizes, by executing the du -s command at the command line. For example:
```
du -s /u01/app/oracle/* 
```
This value provides information about how much space to allocate for the target database system. Check the name and sizes of data files by querying the V$DATAFILE and V$TEMPFILE dynamic views.

If you are using Oracle Automatic Storage Management (ASM), then check the data files used by ASM. As the Grid software owner, log in to the ASMCMD tool and then enter the following commands. In this example, DATA is the location of the data files and RECO is the location of the fast recovery area disk group.
```
du DATA/db_unique_name/
du RECO/db_unique_name/
```
Determine the workload level.

You can generate an Oracle Automatic Workload Repository report to find a sample of the workload for the source database. Alternatively, if you have an Oracle Diagnostics Pack and Oracle Tuning Pack license, you can generate an Automatic Database Diagnostic Monitor report to find the source database performance over a period of time between specified snapshots. The time model statistics, operating system statistics, and wait events provide a relatively clear measure of the workload, in terms of the operating system capacity.
Determine the environment variables that have been set in the source database.

You may want to use these same settings in the target database.
Check if the database to be migrated is a non-default, custom database.
Check the database character set.

You can find the database character set by issuing the following query:
```
SELECT * FROM NLS_DATABASE_PARAMETERS;
```
You will need to ensure that the target database will also have this character set.
Determine the disaster recovery plan that is currently in place.

For example, if Oracle Data Guard is already deployed, then you can create a standby database for the migration procedure. (This migration solution will use Oracle Data Guard for the migration.) If off-site backups are used, then you should plan on making a new backup to ship to Oracle Cloud, using Oracle Recovery Manager (RMAN).
Check if you have Oracle GoldenGate configured with this database.

To find information about Oracle GoldenGate, execute the ggsci utility. Oracle GoldenGate is a useful utility that can be used as an alternative migration tool if you do not want to use Oracle Data Guard for the migration. However, this solution does not cover how to perform the migration with Oracle GoldenGate.

Decide on the Best Migration Strategy

After you inventory your environment, you should decide on the best migration strategy.

Consider the following before you begin the migration process:

The best time of day to perform the migration
Downtime requirements
Database size
The source and target database character sets
The source and target database versions
If the source database contains user-defined data types
The source database and the target database platform (endian)
Security considerations
A strategy for large workloads