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Article ID: 117723, created on Oct 4, 2013, last review on May 11, 2014

  • Applies to:
  • Operations Automation 5.4


  1. When logging in to POA/PBA or switching between them, the following error message is displayed:

    Error [unixODBC]FATAL: remaining connection slots are reserved for non-replication superuser connections  
  2. The periodic task 'Synchronize resource usage for instances of APS applications' runs every 5 minutes and often fails with the error message above.

  3. POA database demonstrates many waiting queries to update APS related tables and the 'aps_resource_usage_report' table in particular:

    plesk=# SELECT current_query FROM pg_stat_activity;
     <IDLE> in transaction
     UPDATE "aps_resource_usage_report" SET "last_update_timestamp" = ('1375866990'), "poll_interval" = (0) WHERE ("aps_resource_usage_report"."id") = (17)
     UPDATE "aps_resource_usage_report" SET "last_update_timestamp" = ('1375777289'), "poll_interval" = (0) WHERE ("aps_resource_usage_report"."id") = (11)
    plesk=# SELECT count(*) FROM pg_stat_activity
            WHERE current_query LIKE '%aps_resource_usage_report%';
    (1 row)


Frequent execution of the APS resource synchronization task leads to high load on the POA system database and connections to database are exhausted as the result.


  • Increase period of the periodic task 'Synchronize resource usage for instances of APS applications' e.g. to 1 hour or more to reduce database load.

  • Increase amount of connections to the POA system database:

    • Log into the PostgreSQL server where the POA database s running as root
    • Increase the value of the 'max_connections' parameter in the '/var/lib/pgsql/9.0/data/postgresql.conf' file from the default 100 to e.g. 200 or more
    • Restart the POA and the PostgreSQL services using the following commands on the proper servers (POA Management Node and POA database server):

      /etc/init.d/pem stop

      /etc/init.d/postgresql-9.0 stop

      /etc/init.d/postgresql-9.0 start

      /etc/init.d/pem start

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