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Dynamic finite versioning (DFV) schemes are an effective approach to concurrent transaction and query processing, where a finite number of consistent, but maybe slightly out-of-date, logical snapshots of the database can be dynamically derived for query access. In DFV, the storage overhead for keeping additional versions of changed data to support the logical snapshots and the amount of obsolescence faced by queries are two major performance issues. In this paper, we analyze the performance of DFV, with emphasis on the trade-offs between the storage cost and obsolescence. We develop analytical models based on a renewal-process approximation to evaluate the performance of DFV using M [greater than or equal to] 2 snapshots. Asymptotic closed-form results for high query arrival rates are given for the case of two snapshots. Simulation is used to validate the analytical models and to evaluate the tradeoffs between various strategies for advancing snapshots when M > 2. The results show that 1) the analytical models match closely with simulation; 2) both the storage cost and obsolescence are sensitive to the snapshot-advancing strategies, especially for M > 2 snapshots; and 3) generally speaking, increasing the number of snapshots demonstrates a trade-off between storage overhead and query obsolescence. For cases with skewed access or low update rates, a moderate increase in the number of snapshots beyond two can substantially reduce the obsolescence, while the storage overhead may increase only slightly, or even decrease in some cases. Such a reduction in obsolescence is more significant as the coefficient of variation of the query length distribution becomes larger. Moreover, for very low update rates, a large number of snapshots can be used to reduce the obsolescence to almost zero without increasing the storage overhead. Index Terms - Multiple versions, transaction processing, concurrent transaction and query processing, analytical modeling, renewal process, two-moment approximation, and dynamic finite versioning.

The performance modeling and analysis of disk arrays is challenging due to the presence of multiple disks, large array caches, and sophisticated array controllers. Moreover, storage manufacturers may not reveal the internal algorithms implemented in their devices, so real disk arrays are effectively black-boxes. We use standard performance techniques to develop an integrated performance model that incorporates some of the complexities of real disk arrays. We show how measurement data and baseline performance models can be used to extract information about the various features implemented in a disk array. In this process, we identify areas for future research in the performance analysis of real disk arrays. [ABSTRACT FROM AUTHOR]

Introduction: Wrinkles commonly manifest in various areas of the face as individuals age. This study aimed to assess the association between facial wrinkles and different facial forms., Materials and Methods: An observational, prospective study was conducted on the facial photographs of 400 subjects aged 40-60 years, which were divided into four groups of 100 subjects each: Group 1, square facial form; Group 2, ovoid facial form; Group 3, square tapered facial form; and Group 4, tapered facial form. All groups had almost equal distributions of males and females. Six types of facial wrinkles were studied, namely, forehead, glabellar, canthal, nasolabial, wrinkles at the corner of the mouth, and perioral wrinkles. Analysis of variance (ANOVA) was used for intergroup comparison, and an independent Student's t-test was used to assess gender differences in facial wrinkles., Results: Significant gender differences were observed for forehead wrinkles in Groups 1 and 3, canthal wrinkles in Groups 1 and 2, and right perioral wrinkles in Group 1 (p<0.05). There were non-significant gender differences between right and left-side facial wrinkles (p>0.05). Significant differences between the groups were observed for all facial wrinkles between the right and left sides of the face (p<0.05). There was a significant difference between the groups for the presence of glabellar, corner of the mouth, and perioral wrinkles, with the presence of higher wrinkles in ovoid and tapered facial forms compared to square and square tapered facial forms (p<0.05)., Conclusions: Females had more facial wrinkles than males, predominantly in the forehead region. The least prominent wrinkles were observed in the perioral region of the face. Glabellar, corner of the mouth, and perioral wrinkles were predominantly observed in ovoid and tapered facial forms., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Japatti et al.)