If a UPS does not have sufficient battery power for a graceful server shutdown, what is the most cost-effective solution?

The most cost-effective solution in this scenario is to install an extended battery pack into the UPS. This option directly addresses the issue of insufficient battery power by enhancing the UPS's capacity to provide additional runtime during a power outage. By increasing the battery's reserve, the server can maintain operation long enough for a graceful shutdown, preventing potential data loss or corruption.

Installing a second UPS would significantly increase costs and complexity while not directly solving the immediate power capacity issue of the first unit. Increasing the size of the swapfile or pagefile does not impact the UPS's ability to provide power during an outage and would not facilitate a graceful shutdown in a power failure situation. These adjustments are more related to system memory management rather than power management, making them irrelevant for this specific problem.