PageDescriptor

PageDescriptor is a generic data structure used in software systems to describe a page-sized unit of data or resource. It serves as a compact identifier and descriptor that helps components locate, validate, and manage the page within memory, storage, or a paging framework. The term is used across domains such as operating systems, database engines, file systems, and UI or web frameworks, with domain-specific fields but a common purpose: to describe a discrete piece of storage or memory and its handling constraints.

In memory management, a PageDescriptor typically includes the page number or virtual address, the mapped frame number when the page is resident, and the page size. It also carries protection attributes (read, write, execute) and status flags such as valid/invalid, dirty, and referenced. Additional data may include a reference count, timestamp, or usage hints. The descriptor is used by the page fault handler, the page table layer, and the cache or buffer pool to coordinate loading, eviction, and synchronization of pages.

In storage and databases, a PageDescriptor may reference a buffered page for a file or relation. Fields can include the file or relation identifier, page offset within the file, residency status, pin count, and a dirty bit. In all contexts, the descriptor enables efficient paging, caching, and consistency guarantees.

Design considerations include whether the descriptor is immutable or mutable, thread-safety, serialization, and the trade-offs between metadata overhead and cache locality. PageDescriptors are typically organized in per-process page tables, buffer pools, or cache managers and interact with memory managers, I/O subsystems, and transaction managers.