A transaction follows the two-phase locking (2PL) protocol if all locking operations (read_lock, write_lock) precede the first unlock operation in the transaction.
Such a transaction can be divided into two phases: an expanding or growing (first) phase, during which new locks on items can be acquired but none can be released, and a shrinking (second) phase, during which existing locks can be released but no new locks can be acquired (Elmasri, 2017).
• Review the media piece, Definition of Transaction Management, found in this week’s Learning Resources. (https://mym.cdn.laureate-media.com/2dett4d/Walden/ITEC/ITEC8240/03/01DTM/story_html5.html)
To complete this Assignment:
- Consider the transactions:
T1: R1(A), W1(B)
T2: R2(A), W2(A), W2(B)
Suppose we insert a pair of lock and unlock commands for each element of the database that the transactions can access.
• Explain how many concurrent execution schedules, of the two transactions, follow the 2PL protocol.
• Explain whether there are any serializable schedules of concurrent execution of the two transactions that do not follow the 2PL protocol.
- Consider the following transactions:
T1: R1(A), R1(B), INC1(A), INC1(B)
T2: R2(A), R2(B), INC2(A), INC2(B)
• Explain how many serializable schedules of concurrent execution of the two transactions there are.
• If the order of the increment operations in T2 is reversed, how many serializable schedules of concurrent execution of the two transactions are there?
Romero, D. H., Riggs, S. A., & Ruggero, C. (2015) conducted an inquiry reviewing the experience of student veterans. The level IV descriptive study was created to review the associations of coping skills, family/social support, and psychological symptoms of college student veterans to determine appropriate interventions for the population. One hundred thirty-six student veterans of the U.S. military were included. The participants then completed a background collection survey to gather health history, demographics, military service, and college experience. The authors discovered a lack of association between dependent variables and psychological distress in college student veterans. However, the study proved a significant association between the presence of avoidant behaviors in coping and family/social interactions with symptoms of depression and anxiety. In fact, the authors found avoidant styles of coping to be a strong indicator of posttraumatic stress symptoms. Despite participant use of harmful styles of coping, appropriate use of family/social support buffered the symptoms of depression and anxiety (Romero et al., 2015). The article included confusing and unnecessary hypothesized path models and was difficult to read. The authors discovered family and social support to be an effective bulwark at preventing psychological distress in student veterans. Avoidant coping strategies were discovered to be a hindrance to maintaining mental health. The importance of appropriate and effective coping strategies was highlighted to promote mental health and prevent psychological distress; however, the importance of familial/social support should not be discounted. Schwarzer, Bowler & Cone (2014) examined New York police officers after the September 11th terrorist attack on the World Trade Center. The Level IV longitudinal review analyzed the mental health of police officers who responded to the 9/11 attack and destruction repairs. The sample included 2943 police officers who participated in a minimum of one shift from the day of the terrorist attack to the last day of repairs, on June 30th, 2002. The officers completed two questionnaires to assess stress response symptoms to determine possible posttraumatic stress disorders [PTSD]. The PTSD specific stressor questionnaire combined with exposure level assessments and social integration measurements determined the mental health outcomes. The articles discussed the two-step process interchangeably, however, the rest of the study was concise and logically organized. The authors discovered an association between high levels of exposure with an increase in stress levels however social integration diminished the effect (Schwarzer et al., 2014). Human beings are social creatures who thrive on social interactions; the study performed by Schwarzer et al. (2014) accentuated the positive effects social interaction has on diminishing the negative psychological impact caused by traumatic events. Zawadzki (2015) reviewed the association between rumination and poor psychologi>GET ANSWER