code: @Override
     public void prefill()
     {
        if (isShutdown())
           return;
  
        if (poolConfiguration.isPrefill())
        {
           ManagedConnectionPool mcp = pools.get(getPrefillCredential());
  
           if (mcp == null)
           {
              // Trigger the initial-pool-size prefill by creating the ManagedConnectionPool
              getManagedConnectionPool(getPrefillCredential());
           }
           else
           {
              // Standard prefill request
              mcp.prefill();
           }
        }
     }
docs: Prefill the connection pool