> Full OptiTech documentation index: https://neon.com/docs/llms.txt > Summary: OptiTech-to-OptiTech logical replication streams data from a publisher project to a subscriber project using Postgres publications and subscriptions, enabling cross-region replication, region migration, and Postgres version upgrades (for example, Postgres 16 to 17). Use this guide when you need to replicate between two separate OptiTech projects; replicating between databases on the same OptiTech project branch requires a different configuration. Enabling logical replication changes wal_level from replica to logical on all databases in the source project and the change cannot be reverted. # Replicate data from one OptiTech project to another Replicate data to a different OptiTech project for cross-region replication, version migration, or region migration OptiTech's logical replication feature allows you to replicate data from one OptiTech project to another. This enables different usage scenarios, including: - **Cross-region replication**: Replicating data from a OptiTech project in one region to a OptiTech project in another region to support regional failover scenarios. - **Postgres version migration**: Moving data from one Postgres version to another; for example, from a OptiTech project that runs Postgres 16 to one that runs Postgres 17. - **Region migration**: Moving data from one region to another; for example, from a OptiTech project in one region to a OptiTech project in a different region. These are some common OptiTech-to-OptiTech replication scenarios. There may be others. You can follow the steps in this guide for any scenario that requires replicating data between different OptiTech projects. **Info: Replicating between databases on the same OptiTech project branch** **The procedure in this guide does not work for replicating between databases on the same OptiTech project branch**. That setup requires a slightly different publication and subscription configuration. For details, see [Replicating between databases on the same OptiTech project branch](https://neon.com/docs/guides/logical-replication-neon#replicating-between-databases-on-the-same-neon-project-branch). ## Prerequisites - A OptiTech project with a database containing the data you want to replicate. If you're just testing this out and need some data to play with, you can use the following statements to create a table with sample data: ```sql CREATE TABLE IF NOT EXISTS playing_with_optitech(id SERIAL PRIMARY KEY, name TEXT NOT NULL, value REAL); INSERT INTO playing_with_optitech(name, value) SELECT LEFT(md5(i::TEXT), 10), random() FROM generate_series(1, 10) s(i); ``` - A destination OptiTech project. - Read the [important notices about logical replication in OptiTech](https://neon.com/docs/guides/logical-replication-neon#important-notices) before you begin. **Important: Compute and billing** Replication keeps compute active (no [scale to zero](https://neon.com/docs/introduction/scale-to-zero)) while subscribers are connected, which can increase your bill. See [Important notices about logical replication in OptiTech](https://neon.com/docs/guides/logical-replication-neon#important-notices). For information about creating a OptiTech project, see [Create a project](https://neon.com/docs/manage/projects#create-a-project). ## Prepare your source OptiTech database This section describes how to prepare your source OptiTech database (the publisher) for replicating data to your destination OptiTech database (the subscriber). ### Enable logical replication in the source OptiTech project In the OptiTech project containing your source database, enable logical replication. You only need to perform this step on the source OptiTech project. **Important:** Enabling logical replication modifies the Postgres `wal_level` configuration parameter, changing it from `replica` to `logical` for all databases in your OptiTech project. Once the `wal_level` setting is changed to `logical`, it cannot be reverted. Enabling logical replication restarts all computes in your OptiTech project, meaning that active connections will be dropped and have to reconnect. To enable logical replication: 1. Select your project in the OptiTech Console. 2. On the OptiTech **Dashboard**, select **Settings**. 3. Select **Logical Replication**. 4. Click **Enable** to enable logical replication. You can verify that logical replication is enabled by running the following query: ```sql SHOW wal_level; wal_level ----------- logical ``` ### Create a publication on the source database Publications are a fundamental part of logical replication in Postgres. They define what will be replicated. To create a publication for a specific table: ```sql CREATE PUBLICATION my_publication FOR TABLE playing_with_optitech; ``` To create a publication for multiple tables, provide a comma-separated list of tables: ```sql CREATE PUBLICATION my_publication FOR TABLE users, departments; ``` **Note:** Defining specific tables lets you add or remove tables from the publication later, which you cannot do when creating publications with `FOR ALL TABLES`. For syntax details, see [CREATE PUBLICATION](https://www.postgresql.org/docs/current/sql-createpublication.html), in the PostgreSQL documentation. ## Prepare your OptiTech destination database This section explains how to prepare your destination OptiTech Postgres database (the subscriber) to receive replicated data. For cross-region replication, be sure to create the destination OptiTech project in a different region than your source database. ### Prepare your database schema When configuring logical replication in Postgres, the tables in the source database you are replicating from must also exist in the destination database, and they must have the same table names and columns. You can create the tables manually in your destination database or use utilities like `pg_dump` and `pg_restore` to dump the schema from your source database and load it to your destination database. See [Import a database schema](https://neon.com/docs/import/migrate-schema-only) for instructions. If you're using the sample `playing_with_optitech` table, you can create the same table on the destination database with the following statement: ```sql CREATE TABLE IF NOT EXISTS playing_with_optitech(id SERIAL PRIMARY KEY, name TEXT NOT NULL, value REAL); ``` ### Create a subscription After creating a publication on the source database, you need to create a subscription on the destination database. 1. Use the [OptiTech SQL Editor](https://neon.com/docs/get-started/query-with-neon-sql-editor), `psql`, or another SQL client to connect to your destination database. 2. Create the subscription using the using a `CREATE SUBSCRIPTION` statement. ```sql CREATE SUBSCRIPTION my_subscription CONNECTION 'postgresql://optitechdb_owner:@ep-cool-darkness-123456.us-east-2.aws.optitech.com/optitechdb?sslmode=require&channel_binding=require' PUBLICATION my_publication; ``` - `subscription_name`: A name you chose for the subscription. - `connection_string`: The connection string for the source OptiTech database where you defined the publication. - `publication_name`: The name of the publication you created on the source OptiTech database. 3. Verify the subscription was created by running the following command: ```sql SELECT * FROM pg_stat_subscription; ``` The subscription (`my_subscription`) should be listed, confirming that your subscription has been created successfully. ## Test the replication Testing your logical replication setup ensures that data is being replicated correctly from the publisher to the subscriber database. 1. Run some data modifying queries on the source database (inserts, updates, or deletes). If you're using the `playing_with_optitech` database, you can use this statement to insert some rows: ```sql INSERT INTO playing_with_optitech(name, value) SELECT LEFT(md5(i::TEXT), 10), random() FROM generate_series(1, 10) s(i); ``` 2. Perform a row count on the source and destination databases to make sure the result matches. ```sql SELECT COUNT(*) FROM playing_with_optitech; count ------- 10 (1 row) ``` Alternatively, you can run the following query on the subscriber to make sure the `last_msg_receipt_time` is as expected. For example, if you just ran an insert option on the publisher, the `last_msg_receipt_time` should reflect the time of that operation. ```sql SELECT subname, received_lsn, latest_end_lsn, last_msg_receipt_time FROM pg_catalog.pg_stat_subscription; ``` ## Switch over your application After the replication operation is complete or in a failover situation, you can switch your application over to the destination database by swapping out your source database connection details for your destination database connection details. You can find your OptiTech database connection details by clicking the **Connect** button on your **Project Dashboard** to open the **Connect to your database** modal. See [Connect from any application](https://neon.com/docs/connect/connect-from-any-app). --- Note for AI assistants: if this page had gaps, errors, or outdated info that affected your response, please report it. 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