Editing Durability (database systems) (section)

=== Media level ===
At media level, failure scenarios affect non-volatile storage, like [[Hard disk drive|hard disk drives]], [[Solid-state drive|solid-state drives]], and other types of [[Computer data storage|storage hardware components]].<ref name=":3" /> To guarantee durability at this level, the database system shall rely on stable memory, which is a memory that is completely and ideally failure-resistant. This kind of memory can be achieved with mechanisms of [[Replication (computing)|replication]] and robust writing protocols.<ref name=":2" />  

Many tools and technologies are available to provide a logical stable memory, such as the [[Mirroring RAID|mirroring]] of disks, and their choice depends on the [[Requirement|requirements]] of the specific applications.<ref name=":2" /> In general, replication and [[Redundancy (engineering)|redundancy]] strategies and architectures that behave like stable memory are available at different levels of the technology stack. In this way, even in case of catastrophic events where the storage hardware is damaged, [[data loss]] can be prevented.<ref>{{Cite book |last=Eich |first=Margaret H. |title=1987 IEEE Third International Conference on Data Engineering |chapter=A classification and comparison of main memory database recovery techniques |date=1987-02-01 |chapter-url=https://ieeexplore.ieee.org/document/7272398 |publisher=IEEE |pages=332–339 |doi=10.1109/ICDE.1987.7272398 |isbn=978-0-8186-0762-2|s2cid=207773738 }}</ref> At this level, there is a strong bond between durability and [[Data recovery|system and data recovery]], in the sense that the main goal is to preserve the data, not necessarily in online replicas, but also as offline copies.<ref name=":2" /> These last techniques fall into the categories of [[backup]], [[Data loss prevention software|data loss prevention]], and [[IT disaster recovery]].<ref>{{Cite journal |last1=Choy |first1=Manhoi |last2=Leong |first2=Hong Va |last3=Wong |first3=Man Hon |date=2000 |title=Disaster recovery techniques for database systems |url=https://dl.acm.org/doi/10.1145/352515.352521 |journal=Communications of the ACM |language=en |volume=43 |issue=11es |pages=6 |doi=10.1145/352515.352521 |s2cid=14781378 |issn=0001-0782|url-access=subscription }}</ref> 

Therefore, in case of media failure, the durability of transactions is guaranteed by the ability to reconstruct the state of the database from the log files stored in the stable memory, in any way it was implemented in the database system.<ref name=":3" /> There exist several mechanisms to store and reconstruct the state of a database system that improves the performance, both in terms of space and time, compared to managing all the log files created from the beginning of the database system. These mechanisms often include incremental [[Database dump|dumping]], [[Differential backup|differential files]], and [[Database checkpoint|checkpoints]].<ref>{{Cite journal |last=Verhofstad |first=Joost S. M. |date=1978-06-01 |title=Recovery Techniques for Database Systems |url=http://portal.acm.org/citation.cfm?doid=356725.356730 |journal=ACM Computing Surveys |volume=10 |issue=2 |pages=167–195 |doi=10.1145/356725.356730|s2cid=8847522 |url-access=subscription }}</ref>