Incremental Synchronization Error: remaining connection slots are reserved

Scenarios

During incremental synchronization, an error is reported, and the log information is as follows: service INCREMENT failed, cause by: Unable to connect to DBMS: url= %s user= %s, Caused by: FATAL: remaining connection slots are reserved for non-replication superuser connections.

Possible Causes

• The number of user connections to the destination database reaches the upper limit. As a result, the connection to the destination database fails to be established.
  

  Log in to the destination RDS PostgreSQL database and run the following SQL statement:

  • View max_connections.

    show max_connections;

  • Check the current number of connections.

    select count(*) from pg_stat_activity;

Solution

On the destination RDS PostgreSQL database console, change the value of max_connections to a larger value and make it take effect. Each DRS task requires about 100 connections.