Presentation is loading. Please wait.

Presentation is loading. Please wait.

William Easton. Introduction  Mobile Environments  Locking and Data Starvation  Mobile DB Architecture  Timing Mechanisms  Static Timer  Dynamic.

Similar presentations


Presentation on theme: "William Easton. Introduction  Mobile Environments  Locking and Data Starvation  Mobile DB Architecture  Timing Mechanisms  Static Timer  Dynamic."— Presentation transcript:

1 William Easton

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


Download ppt "William Easton. Introduction  Mobile Environments  Locking and Data Starvation  Mobile DB Architecture  Timing Mechanisms  Static Timer  Dynamic."

Similar presentations


Ads by Google