1 / 14

Strategy to reduce rollbacks in mobile environments

William Easton. Strategy to reduce rollbacks in mobile environments. Introduction. Mobile Environments Locking and Data Starvation Mobile DB Architecture Timing Mechanisms Static Timer Dynamic Timer Preemptive Timer. Mobile Environments. Prone to Connection loss Timeouts

hye
Download Presentation

Strategy to reduce rollbacks in mobile environments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. William Easton Strategy to reduce rollbacks in mobile environments

  2. Introduction • Mobile Environments • Locking and Data Starvation • Mobile DB Architecture • Timing Mechanisms • Static Timer • Dynamic Timer • Preemptive Timer

  3. Mobile Environments • Prone to • Connection loss • Timeouts • Loss of bandwidth • Reduced storage • Limited battery power All these contribute to the frequency of failures of mobile databases.

  4. Data Starvation • Phone connects and locks data • Phone disconnects • Phone holds that lock (indefinitely) • Other mobile devices cannot access that information • These locking strategies are good for traditional databases but are not optimal for mobile

  5. Mobile DB Architecture • Mobile host • Fixed host • Mobile host may not always be connected to the fixed host

  6. Timing Mechanisms • Static timer • A transaction must commit before the timer is finished • If not the transaction is aborted and locked data is aquired by the next mobile host attempting to access the information • Dynamic Timer • The solution this paper introduces

  7. Dynamic Timer • Starts off with specified timer • As transactions are executed it changes according to how they are being executed • If transactions are running past the timer and are rolled back then the timer is increased slightly

  8. Dynamic Timer • So processes that would’ve unsuccessfully processed earlier might be able to be completed • Leads to fewer rollbacks • There has to be a catch • Larger overhead • Processes in the queue will have to wait longer to access the data they need • There is a threshold time that the dynamic timer cannot surpass

  9. Dynamic Timer This is an activity diagram from the paper to depict how the timer will be adjusted.

  10. Static Timer

  11. Dynamic Timer

  12. Preemptive Timer

  13. Final Metrics • Timeout(static) • Dynamic • Preemption • Overall the preemptive has the best commit rate with the least time but does require the knowledge of execution times

  14. Questions • Mobile environments • Static methods • Dynamic method • Preemptive method • Conclusions

More Related