## 6 Performance Evaluation
### Experimental Environments  
The specific experimental environment commonly applied to the two file-access scenarios mentioned above is as follows. The access experiment was conducted with 10 test files of the same size generated with 1 MB of random bytes. Actual 1 s is assumed to be 1 h in the experimental environment, and the total file access experiment period is 6 days. That is, the actual time to perform one experiment of the file access scenario is 144 s (= 24 \(\times\) 6). The file access operations performed during the first 3 days and the last 3 days of the experiment differ depending on the scenario, which will be described in detail in the experimental environment of each scenario. Table 2 shows the default values of parameters used by the active file mode change mechanism in both experimental scenarios. Figure 7: Flow chart of local mode change. Directory activation monitoring period (_DAMP_) is the period at which the active file mode change mechanism calculates the directory activation ratio. Every 11 h after the start of the file access experiment, the active file mode change mechanism calculates the directory activation ratio and determines whether to change the file mode based on this value. File synchronization storage (\(FSS\)) represents the total amount of local storage allocated for file synchronization and is required when calculating the storage usage ratio in the experiment. This value may be the total capacity of the client's local storage, or it may be set to an arbitrary value smaller than this. In this experiment, we set the default value as 10 MB. Duration since last access threshold (_DSLAT_) is the threshold of time elapsed since the last access of a file, indicating the length of time the file activation ratio remains at its maximum value of 1 since the last access of the file. In this experiment, we set the default value to 36 h, which means that the file activation ratio remains at 1 for a day and a half (36 h) after the file is accessed. If there is no file access after this threshold, the file activation ratio starts to decrease in proportion to the time elapsed after this threshold. Online mode threshold (\(OMT\)) is the online mode threshold, which is a criterion for determining whether the active file mode change mechanism initiates the online mode change operation. If the directory activation ratio is less than the _OMT_, the active file mode change mechanism starts to change the selected files to the online mode. In this experiment, we set the _OMT_ to 0.5. Local model threshold (_LMT_) is the local mode threshold. This threshold is the criterion by which the active file mode change mechanism decides whether to change files to the local mode. If the directory activation ratio is greater than the _LMT_, the active file mode change mechanism starts the local mode change operation. As with _OMT_, we also set the _LMT_ to 0.5 in this experiment. Used storage ratio threshold (_USRT_) is the local storage usage ratio threshold. The _USRT_ plays a role in regulating the local storage usage ratio so that the active file mode change mechanism can change files to the online or local mode under the _USRT_ limit. In this experiment, we set the default value of the _USRT_ to 0.5. For example, when the active file mode change mechanism changes files to the online mode, the change is only performed until the local storage usage is less than or equal to 5 MB, which is 50% of the total amount of 10 MB. When the mechanism changes files to the local mode, it limits the changes to only until the local storage usage is greater than 5 MB. Maximum access delay threshold (_MADT_) is used as a criterion for determining the minimum size of an online mode file to be changed to the local mode. In this experiment, we set the _MADT_ to 0, which means that the active file mode change mechanism only considers the last access time, not the minimum size, when selecting a file to change to the local mode.