Which four factors can influence the rate of SQL apply on a logical standby database?
A.
the size of the undo tablespace on the logical standby database
B.
the number of full table scans performed by SQL apply
C.
the number of coordinator processes on the standby database instance
D.
the size of the shared pool
E.
the number of APPLIER processes
F.
the number of PREPARER processes
Explanation:
B: If a table still does not have any unique index specified on the logical standby database, this may cause
UPDATE statements to do full table scans on the logical standby database. You can remedy that by adding a
unique index on the a column on the logical standby database.
E: SQL Apply uses a collection of background processes to apply changes from the primary database to the
logical standby database.
During apply processing:
* The ANALYZER process identifies dependencies between different transactions.
* The COORDINATOR process (LSP) assigns transactions to different appliers and coordinates among them
to ensure that dependencies between transactions are honored.
* The APPLIER processes applies transactions to the logical standby database under the supervision of the
coordinator process.
F: The PREPARER process is used during the log mining process, which is part of the SQL apply process.
D: The Shared Pool is used by the preparar and Builder proccesses.
Figure: SQL Apply Processing
Incorrect Answers:
C: There is only one coordinator process.
https://docs.oracle.com/cd/B28359_01/server.111/b28294/manage_ls.htm
B,D,E,F
– On the primary database, if a table does not have a primary key or a unique index and you are certain the rows are unique, then create a primary key RELY constraint. On the logical standby database, create an index on the columns that make up the primary key. By creating an index on the following tables, performance can be improved significantly.
– Adjusting the number of APPLIER processes will help you achieve greater throughput In rare cases do you need to adjust the number of PREPARER processes. Before you decide to increase the number of PREPARER processes.
– Adjust memory used by Logical Change Record (LCR) cache by increasing SGA. LCR cache is a structure in SGA, a portion of the shared pool size.
– Statistics should be gathered on the standby database because the cost-based optimizer (CBO) uses them to determine the optimal query execution path. New statistics should be gathered after the data or structure of a schema object is modified in ways that make the previous statistics inaccurate.
– By default transactions are applied on the logical standby database in the exact order in which they were committed on the primary database. However, many applications do not require such strict ordering among all transactions. Adjusting strict ordering typically results in higher apply rates at the logical standby database.
https://docs.oracle.com/database/121/SBYDB/manage_ls.htm#SBYDB4839