# Quantum Game Application to Recovery Problem in Mobile Database
## 2 State-of-the-Art  
In recent years, mobile application failure recovery has grown in popularity. The suggested solutions use checkpointing, logging, or a combination of the two, while taking into account the inherent constraints of the mobile computing environment. Much research is based on a distributed uncoordinated checkpointing method, in which several MHs may achieve a globally consistent checkpoint without depending on coordination messages. Others presented a checkpointing-only method, which offers globally consistent checkpoints without requiring additional communications but is unique in that it uses time to synchronize checkpoint creation. The authors of [22] described a technique for mobile database applications to recover from checkpointing and logging failures depending on mobility. Current methods use periodic checkpoints that are not dependent on user mobility. This system initiates checkpoints only after a certain number of mobility handoffs has occurred. The failure, log arrival, and mobility rates of the mobile host determine the optimum threshold. This enables modification of the checkpointing rate on a per-user basis. Additionally, depending on the checkpoint frequency, the last checkpoint may be situated a considerable distance from the mobile support station (MSS). Additionally, a significant number of logs across several MSSs may be scattered, resulting in a lengthy recovery time. The authors of [23] suggested a technique for recovering applications in a mobile computing environment by combining movement-based checkpoints with message recording. A node's adaptability is used to decide if a checkpoint should be taken. This method was developed using a variety of factors, including the number of MH registrations in an area, the number of regions, and the number of handoffs. This approach is especially beneficial in large networks with many areas. In contrast, operating in restricted areas may result in extra expenses. The authors of [24] developed a rollback recovery method that prioritized separate checkpoints and message recording. The algorithm is unique in that it manages message logs and checkpoints through mobile agents. Additionally, if a mobile node travels a great distance from its most recent checkpoint, the agents are able to move the checkpoint and message logs stored in distant mobile service stations. Thus, the time needed to retrieve a mobile node would never exceed a specified threshold. It is feasible to keep just one checkpoint in permanent storage by recording messages. The main advantage of this study is the modest size of the message log, which cannot be very large owing to the network's low message substitution rate. Additionally, if a process interacts often, it may decrease its checkpointing interval. Nonetheless, this method occurs in a small number of situations, resulting in increased network activity during recovery. Specifically, if the length of the mobility profile exceeds the number of different mobile service stations at any point, the logs must be consolidated into a single place. The authors in [25] prepared a proposal for a contemporary checkpointing method that is suitable for mobile computing systems. This method is characterized by its dependability and efficiency in terms of time-space overhead associated with checkpointing and normal application execution. The work presented in [26] suggested a log management and low-latency no-blocking checkpointing system that utilizes a mobile-agent-based architecture to reduce recovery time. By decreasing the amount of messages sent, this protocol reduced recovery time. On the contrary, particularly when many agents are needed, it may result in an increase in complexity, which may absorb some of the extra execution costs. The authors of [27] developed a log management strategy for mobile computing systems that substantially lowers the total cost of failure recovery when compared to existing lazy and pessimistic approaches.