How to load data from IBM Db2 to Postgres destination

Ensure that both the IBM DB2 and PostgreSQL database servers are properly installed and configured on their respective systems. Install the required database drivers and command-line tools for both DBMSs.

Before you can move data, you need to recreate the DB2 schema in PostgreSQL. This involves creating tables, indexes, views, and other database objects.

1. Extract the DB2 database schema:

Use the `db2look` utility to extract the database schema from DB2:

```sh

db2look -d your_db2_database -e -o db2_schema.sql

```

This command will generate a SQL file `db2_schema.sql` with the DDL statements for the DB2 database.

2. Modify the schema for PostgreSQL compatibility:

Edit the `db2_schema.sql` file to make it compatible with PostgreSQL. This may involve changing data types, removing DB2-specific syntax, and adjusting SQL functions and stored procedures.

3. Create the PostgreSQL schema:

Execute the modified schema SQL script against your PostgreSQL database to create the schema:

```sh

psql -U postgres_user -d postgres_database -f modified_db2_schema.sql

```

You will need to export the data from DB2 into a format that can be imported into PostgreSQL.

1. Export the data using the `db2export` command:

```sh

db2 "export to tablename.ixf of ixf messages tablename.msg select * from tablename"

```

Replace `tablename` with the actual table name. The `.ixf` format is a proprietary IBM format, but we will convert it in the next step.

2. Convert the .ixf file to a delimited format (e.g., CSV):

Use the `db2` command line or a custom script to convert the `.ixf` files to a CSV format that PostgreSQL can understand.

Now that you have the data in a CSV format, you can import it into PostgreSQL.

1. Copy the CSV files to the PostgreSQL server:

Use `scp`, `ftp`, or any other file transfer method to move the CSV files to the PostgreSQL server.

2. Import the data using the `psql` command:

Use the `\copy` command within `psql` to import the data:

```sh

psql -U postgres_user -d postgres_database

\copy tablename from 'tablename.csv' with (format csv, header true, delimiter ',');

```

Replace `tablename.csv` with the actual CSV filename and adjust the delimiter and header options as needed.

After importing the data, it's essential to verify that the data has been transferred correctly.

1. Check record counts:

Compare the record counts in both DB2 and PostgreSQL for each table to ensure they match.

2. Perform data checks:

Execute queries to check for data consistency and integrity between the source DB2 and target PostgreSQL databases.

3. Check for errors:

Review the import logs for any errors or warnings that may indicate issues with the data import.

Once you're satisfied with the data integrity, you can finalize the migration by:

1. Updating sequences:

If you have any auto-increment columns, update the sequences in PostgreSQL to reflect the current state.

2. Performing optimizations:

Analyze the tables and indexes in PostgreSQL to optimize their performance.

3. Testing applications:

Update your application connection strings and thoroughly test your applications with the new PostgreSQL database.

After the migration is successfully completed and verified, clean up any temporary files or scripts used during the migration process.