The Site Recovery Manager Server requires its own database, which it uses to store data such as recovery plans and inventory information.
Site Recovery Manager provides an embedded vPostgreSQL database that requires fewer steps to configure than an external database. The embedded vPostgreSQL database can support a full-scale Site Recovery Manager environment. You can select the option to use the embedded database when you install Site Recovery Manager. The Site Recovery Manager installer creates the embedded database and a database user account according to the information that you specify during installation.
You can also use an external database. If you use an external database, you must create the database and establish a database connection before you can install Site Recovery Manager.
Site Recovery Manager cannot use the vCenter Server database because it has different database schema requirements. You can use the vCenter Server database server to create and support the Site Recovery Manager database.
Each Site Recovery Manager site requires its own instance of the Site Recovery Manager database. Use a different database server instance to run the individual Site Recovery Manager databases for each site. If you use the same database server instance to run the databases for both sites, and if the database server experiences a problem, neither Site Recovery Manager site will work and you will not be able to perform a recovery.
Site Recovery Manager does not require the databases on each site to be identical. You can run different versions of a supported database from the same vendor on each site, or you can run databases from different vendors on each site. For example, you can run different versions of Oracle Server on each site, or you can have an Oracle Server database on one site and the embedded database on the other.
If you are updating Site Recovery Manager to a new version, you can use the existing database. Before you attempt an upgrade, make sure that both Site Recovery Manager Server databases are backed up. Doing so helps ensure that you can revert back to the previous version after the upgrade, if necessary.
For the list of database software that Site Recovery Manager supports, see the Compatibility Matrixes for vCenter Site Recovery Manager 5.8 at https://www.vmware.com/support/srm/srm-compat-matrix-5-8.html.