The performance of MySQL and PostgreSQL agents can vary widely depending on the design of the database/instance being monitored. The higher the number of objects the more data is collected by the agents.
Some general recommendations include the following:In the Agent Status Properties of the database agents
1). Disable the Dynamic Memory Allocation checkbox of all of the MySQL and PostgreSQL agents
2). In the PostgreSQL Top Table Collection, reduce the # of Top Tables (per DB) from the default value of 100 to a lower value and sort by Total Table Size
3). Reduce the # of top statements from the default 200 (PostgreSQL) and 1000 (MySQL) to 50
4). Reduce the Table/Index/Function collection intervals from five minutes (300 seconds) to six hours (21,600 seconds) in PostgreSQL and from 30 minutes (1800 seconds) to six hours (21,600 seconds) in MySQL.