Nonpagable

Nonpagable (often written as nonpageable) memory is a portion of a computer’s physical RAM that the operating system designates as non-pageable. It cannot be swapped out to disk and remains resident in memory regardless of overall RAM pressure. This is in contrast to pageable memory, which may be moved to secondary storage and later restored.

Nonpageable memory is used for code and data that must stay in RAM to function correctly, especially in kernel mode or during high-priority operations. It typically covers kernel data structures, driver code and data, interrupt handling components, and other objects that require deterministic access times and stability. Keeping these elements resident helps prevent latency and avoids system hangs in critical execution paths.

Implementation and management vary by operating system. In Windows, the concept is implemented as the nonpaged pool, a defined portion of RAM reserved for kernel and driver objects that cannot be paged out. The pool is divided into nonpaged and paged segments, and its size is established at boot. If nonpaged pool is exhausted, system stability can be affected and certain kernel operations may fail. Other systems use analogous mechanisms, such as locked or non-swappable memory, to ensure critical data remains in RAM.

Monitoring nonpagable memory helps diagnose performance and stability issues. OS-specific tools report nonpaged usage and total pool size, and administrators may adjust configurations, update drivers, or optimize memory usage to mitigate pressure on the nonpaged area. Excessive reliance on nonpaged memory can reduce overall available RAM and impact system performance.

Related terms include pageable memory, memory pool, and locked/non-swappable memory. Nonpagable memory is a foundational concept in memory management, balancing the needs for fast, reliable access to critical components with the limits of physical RAM.