Semipersistent

Semipersistent is an adjective used in information technology to describe states, data, or resource allocations that are maintained for a defined, limited period rather than indefinitely or only for a single operation. The exact duration and conditions for persistence are policy-driven and can depend on system design, traffic characteristics, or fault-tolerance requirements. In practice, semipersistence is a middle ground between volatile, ephemeral data and fully persistent storage.

In mobile and wireless networks, semi-persistent scheduling (SPS) is a mechanism used in LTE and 5G to allocate radio resources to a user equipment (UE) for a sequence of transmission opportunities. SPS reduces signaling overhead by pre-allocating resources for a period, after which the resources are released or can be reconfigured. This is beneficial for periodic and low-latency traffic such as voice. Implementation details vary by standard, but the core idea is that grants persist across multiple frames rather than being renegotiated for every transmission.

In computing and storage, semipersistent memory or caching refers to data retained across multiple operations or requests for a defined duration, often managed by expiration rules or TTL (time-to-live). For example, a cache may maintain hot objects for several minutes to reduce latency, after which they are evicted if not accessed or if memory pressure occurs. Semipersistent arrangements balance fast access with resource constraints and resilience to failure or restart; they are not guaranteed to survive power loss or reboot.

Because the term is context-dependent, semipersistent is not a standardized concept with a single formal definition. It is commonly used to describe policies or mechanisms that sit between fully transient and fully persistent behavior, emphasizing predictable, bounded persistence.