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2.2. Eviction Strategies
Each eviction strategy has specific benefits and use cases, as outlined below:
| Strategy Name | Operations | Details |
|---|---|---|
EvictionStrategy.NONE | No eviction occurs. | This is the default eviction strategy in Red Hat JBoss Data Grid. |
EvictionStrategy.LRU | Least Recently Used eviction strategy. This strategy evicts entries that have not been used for the longest period. This ensures that entries that are reused periodically remain in memory. | |
EvictionStrategy.UNORDERED | Unordered eviction strategy. This strategy evicts entries without any ordered algorithm and may therefore evict entries that are required later. However, this strategy saves resources because no algorithm related calculations are required before eviction. | This strategy is recommended for testing purposes and not for a real work implementation. |
EvictionStrategy.LIRS | Low Inter-Reference Recency Set eviction strategy. | LIRS is an eviction algorithm that suits a large variety of production use cases. |
2.2.1. LRU Eviction Algorithm Limitations
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In the Least Recently Used (LRU) eviction algorithm, the least recently used entry is evicted first. The entry that has not been accessed the longest gets evicted first from the cache. However, LRU eviction algorithm sometimes does not perform optimally in cases of weak access locality. The weak access locality is a technical term used for entries which are put in the cache and not accessed for a long time and entries to be accessed soonest are replaced. In such cases, problems such as the following can appear:
- Single use access entries are not replaced in time.
- Entries that are accessed first are unnecessarily replaced.
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