# Prerequisites

The following section describes the prerequisites for working with the Google Cloud AlloyDB for PostgreSQL source endpoint.[](https://help.qlik.com/en-US/replicate/Content/Replicate/Main/AlloyDBforPostgreSQLSource/prereq_postgresql_source.htm)

## Drivers and libraries

### Replicate for Windows

Install PostgreSQL ODBC Driver psqlodbc\_13\_xx\_xxxx-x64 on the Replicate machine.

Information noteMake sure to add the psql.exe path (for example, "C:\Program Files\PostgreSQL\13xx\bin") to the system PATH.

### Replicate for Linux

Download PostgreSQL 13 ODBC driver, and client programs and libraries.

* Example PostgreSQL ODBC file name: postgresql13-odbc-13.02.0000-1PGDG.rhel8.x86\_64.rpm
* PostgreSQL client programs and libraries file name: postgresql13-13.8-1PGDG.rhel<version>.x86\_64.rpm

Then, open a shell prompt and do the following:

1. Stop the Replicate service and optionally confirm that it has stopped as described in [Replicate server procedures](https://help.qlik.com/en-US/replicate/November2024/Content/Replicate/Main/Installation/Server_Procedures.htm).

2. Install PostgreSQL 13 client programs and libraries.

3. Install the ODBC driver for PostgreSQL 13.

4. Change the working directory to <Replicate-Install-Dir>/bin.

5. Copy the driver location to the `site_arep_login.sh` file:

   `echo "export LD_LIBRARY_PATH=\$LD_LIBRARY_PATH:/usr/lib:/usr/lib64:/usr/pgsql-13/lib" >> site_arep_login.sh`

   This will add the driver to "LD\_LIBRARY\_PATH" and update the driver location in the site\_arep\_login.sh file.

6. Optionally, confirm that the driver location was copied:

   ```
   cat site_arep_login.sh
                           
   ```

7. Makes sure that the `/etc/odbcinst.ini` file contains an entry for PostgreSQL, as in the following example:

   `[PostgreSQL]`

   `Description = PostgreSQL ODBC driver`

   `Driver = /usr/pgsql-13/lib/psqlodbc.so`

   `Setup = /usr/pgsql-13/lib/psqlodbcw.so`

   `UsageCount = 1`

8. Start the Replicate service and optionally confirm that it has started as described in [Replicate server procedures](https://help.qlik.com/en-US/replicate/November2024/Content/Replicate/Main/Installation/Server_Procedures.htm).

## Prerequisites for capturing changes

To be able to capture changes from the database, you need to set up logical replication.

To do this:

1. On Google Cloud platform, set the following flags in the AlloyDB settings:

   * alloydb.logical\_decoding=on
   * max\_replication\_slots: Every task creates a new slot; this parameter configures the amount of simultaneous connections that can be established to the database. If you encounter performance issues, increasing this value might help.
   * max\_wal\_senders: The number of tasks that can run in parallel. If you encounter performance issues, increasing this value might help.

   For more information on these parameters, see https://www.postgresql.org/docs/current/runtime-config-replication.html

2. On the database, alter the Replicate user to be able to work with replication:

   ALTER USER replicate-user WITH REPLICATION;

   Where replicate-user is the user specified in the endpoint settings.

## Required permissions

The user specified in the endpoint connection settings must be granted the following permissions on the PostgreSQL database:

* For Full Load tasks: Standard SELECT

* For CDC tasks: alloydbsuperuser

  See also [Using an account without the "superuser" role](https://help.qlik.com/en-US/replicate/November2024/Content/Replicate/Main/AlloyDBforPostgreSQLSource/non_superuser.htm).