Which three statements are true about using the in Memory (IM) column store?
Correct Answer: C,E,F
The Oracle In-Memory (IM) column store feature enhances the performance of databases by providing a fast columnar storage format for analytical workloads while also potentially benefiting OLTP workloads. * C (True): It can improve OLTP workload performance by providing a faster access path for full table scans and reducing the need for indexes in certain scenarios, as the In-Memory store allows for efficient in-memory scans. * E (True): The In-Memory column store does not require all database data to fit in memory. It can be used selectively for performance-critical tables or partitions, and Oracle Database will manage the population and eviction of data as needed. * F (True): In-Memory column store can significantly improve performance for queries joining several tables, especially when bloom filters are used, as they are highly efficient with the columnar format for large scans and join processing. The other options provided are not correct in the context of the In-Memory column store: * A (False): While In-Memory column store is designed for analytical queries rather than caching results of function evaluations, it does not specifically avoid improving performance for queries using cached results of function evaluations. * B (False): In-Memory column store can improve the performance of queries that use join groups, which can be used to optimize joins on columns from different tables. * D (False): In-Memory column store can improve the performance of queries using expressions, including user-defined virtual columns, because it supports expression statistics which help in optimizing such queries. References: * Oracle Database In-Memory Guide: In-Memory Column Store in Oracle Database * Oracle Database In-Memory Guide: In-Memory Joins * Oracle Database In-Memory Guide: In-Memory Aggregation
Question 2
Which statement is true about DB time in V$$YS_TIME_MODEL?
Correct Answer: B
DB time includes the time spent on user and background processes. It can be greater than the elapsed time because it accumulates the active time of all the processes. For example, if two sessions are each active for 2 seconds at the same time, DB time would accumulate 4 seconds, while the elapsed time would be only 2 seconds.References: * Oracle Database Performance Tuning Guide, 19c * Oracle Database Reference, 19c
Question 3
Examine this statement and output: Which two situations can trigger this error?
Correct Answer: A,E
The ORA-15505 error indicates that the instance encountered errors while trying to access the specified directory. This could be due to: A: Insufficient privileges: The user attempting to start the workload capture might not have the required permissions to execute the DBMS_WORKLOAD_CAPTURE package or to read/write to the directory specified. E: Accessibility: The database instance may not be able to access the directory due to issues such as incorrect directory path, directory does not exist, permission issues at the OS level, or the directory being on a file system that's not accessible to the database instance. References: * Oracle Database Error Messages, 19c * Oracle Database Administrator's Guide, 19c
Question 4
Which three statements are true about using the in Memory (IM) column store?
Correct Answer: C,E,F
The Oracle In-Memory (IM) column store feature enhances the performance of databases by providing a fast columnar storage format for analytical workloads while also potentially benefiting OLTP workloads. * C (True):It can improve OLTP workload performance by providing a faster access path for full table scans and reducing the need for indexes in certain scenarios, as the In-Memory store allows for efficient in-memory scans. * E (True):The In-Memory column store does not require all database data to fit in memory. It can be used selectively for performance-critical tables or partitions, and Oracle Database will manage the population and eviction of data as needed. * F (True):In-Memory column store can significantly improve performance for queries joining several tables, especially when bloom filters are used, as they are highly efficient with the columnar format for large scans and join processing. The other options provided are not correct in the context of the In-Memory column store: * A (False):While In-Memory column store is designed for analytical queries rather than caching results of function evaluations, it does not specifically avoid improving performance for queries using cached results of function evaluations. * B (False):In-Memory column store can improve the performance of queries that use join groups, which can be used to optimize joins on columns from different tables. * D (False):In-Memory column store can improve the performance of queries using expressions, including user-defined virtual columns, because it supports expression statistics which help in * optimizing such queries. References: * Oracle Database In-Memory Guide:In-Memory Column Store in Oracle Database * Oracle Database In-Memory Guide:In-Memory Joins * Oracle Database In-Memory Guide:In-Memory Aggregation
Question 5
A database instance is suffering poor I/O performance on two frequently accessed large tables. No Big Table caching occurs in the database. Examine these parameter settings: Which are two actions either one of which will allow Big Table caching to occur?
Correct Answer: C,D
Big Table caching is a feature that allows frequently accessed large tables to be cached in memory to improve I/O performance. From the parameter settings provided, Big Table caching is not occurring because DB_BIG_TABLE_CACHE_PERCENT_TARGET is set to 10, which is the minimum threshold for enabling the feature, but the size of the cache is too small for the big tables to be effectively cached. To enable Big Table caching, one of the following actions could be taken: * C (Correct): Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to at least 25. This action would allocate a larger percentage of the buffer cache for storing big tables, which could allow for caching large tables and thus improve I/O performance. * D (Correct): Increasing DB_CACHE_SIZE to 1G. Since the size of the buffer cache is a determining factor for how much data can be cached, increasing this parameter would provide more memory space for big tables to be cached. Options A, B, E, and F will not enable Big Table caching because: * A: Increasing DB_BIG_TABLE_CACHE_PERCENT_TARGET to 50 without adjusting the overall size of the cache might still not be sufficient if the DB_CACHE_SIZE is not large enough to hold the big tables. * B: Setting DB_KEEP_CACHE_SIZE to at least 50M only specifies a separate buffer pool for objects with the KEEP cache attribute and does not affect Big Table caching. * E: and F: Changing the PARALLEL_DEGREE_POLICY to ADAPTIVE or AUTO influences the behavior of parallel execution but does not directly enable or influence Big Table caching. References: * Oracle Database Performance Tuning Guide: Big Table Caching * Oracle Database Reference: DB_BIG_TABLE_CACHE_PERCENT_TARGET * Oracle Database Reference: DB_CACHE_SIZE
