Exam 1z0-078 topic 1 question 3 discussion

I think ACE

considering global concurrency control , AEF

I think B,D and E

https://www.dba-oracle.com/real_application_clusters_rac_grid/rac_process.htm

AEF Since the RAC system allows many users to connect and process database SQL operations concurrently, many resources, such as data blocks and enqueues, are used simultaneously. This situation demands an effective synchronization of the concurrent tasks.

BDE or ADE i think BDE

correct answers B,D,E beacuse; Latches and mutexes may only protect access to memory structures if they are accessed by processes in the same instance. In RAC, latches and mutexes are still used, but for global concurrency control, some additional global enqueues are used to provide protection across instances. Oracle requires concurrency control because it is a multi-user system. Single-instance Oracle provides concurrency control: Latches or mutexes for memory structures Enqueues for resource control Buffer cache pins for cache management

Proposed answer is an concept error: mutexes and latches are "intra" instance concurrency control mechanisms. The question is about global concurrency control. RAC course guide page 7-3 states Single-instance oracle provides concurrency control through: - latches or mutexes for memory structures - enqueues for resource control - buffer cache pins for cache management In RAC, structures and resources may be accessed by or modified by a ssession running on any database instance RAC, therefore, requires additional global concurrency controls to mediate access across instances - global locks control library and row cache access --> (cursors) - Global enqueues control resource access - Cache fusion controls buffer cache access --> (database block buffers) So correct answer is: AEF