New Release 1z0-084 Oracle Certification Questions

TheDBMS_STATS.GATHER_DATABASE_STATSprocedure is used to gather statistics for all schema objects in the database that do not have up-to-date statistics. These statistics are essential for the optimizer to make informed decisions about the most efficient way to execute a query. The procedure collects statistics such as table and column statistics, index statistics, and system statistics, which are all used in the execution plan generation.

References:

• Oracle Database PL/SQL Packages and Types Reference, 19c
• Oracle Database Performance Tuning Guide, 19c

The execution plan shows a full table access for theSALEStable. To reduce the execution time, creating an index onSALES.TIME_IDwould be beneficial as it would allow the database to quickly sort and retrieve the most recent sales without the need to perform a full table scan, which is I/O intensive and slower. By indexingTIME_ID, which is used in theORDER BYclause, the optimizer can take advantage of the index to efficiently sort and limit the result set to the ten most recent sales.

• B (Incorrect):ReplacingFETCH FIRSTwithROWNUMwould not necessarily improve the performance unless there is an appropriate index that the optimizer can use to avoid sorting the entire result set.
• C (Incorrect):There is no indication that the current statistics are inaccurate; hence, collecting new statistics may not lead to performance improvement.
• D (Incorrect):While adaptive plans can provide performance benefits by allowing the optimizer to adapt the execution strategy, the main issue here is the lack of an index on theORDER BYcolumn.
• E (Incorrect):Creating an index onSALES.CUST_IDcould improve join performance but would not address the performance issue caused by the lack of an index on theORDER BYcolumn.

References:

• Oracle Database SQL Tuning Guide:Managing Indexes
• Oracle Database SQL Tuning Guide:Using Indexes and Clusters

To transport performance data from an Oracle Database Standard Edition, which uses Statspack, to an Enterprise Edition database, which uses AWR, you must consider the compatibility of data structures and repository schemas between these tools. The recommended method is:

• D (Correct):Export the data using theexputility with a parameter file appropriate for Statspack (likespuexp.par) from the Statspack repository and import it into a dedicated Statspack schema on the destination. Since Statspack and AWR use different schemas, it's not recommended to import Statspack data directly into the AWR repository.

The other options are incorrect because:

• A (Incorrect):expdpis not designed to export from Statspack, andawrloadis intended for loading from an AWR export file, not a Statspack export.
• B (Incorrect):Althoughexpdpandimpdpare used for exporting and importing data, the AWR repository schema is different from the Statspack schema, so importing Statspack data directly into the AWR repository is not recommended.
• C (Incorrect):Usingexpdpto export from Statspack and then importing directly into the AWR repository is not the correct approach due to the schema differences between Statspack and AWR.

References:

• Oracle Database Performance Tuning Guide:Migrating from Statspack to AWR

During a soft parse, Oracle checks the shared SQL area to see if an incoming SQL statement matches one already in the shared pool. This operation includes syntax and semantic checks. The syntax check ensures the statement is properly formed, and the semantic check confirms that all the objects referenced in the SQL statement exist and that the user has the necessary privileges to access them.References:

• Oracle Database Concepts, 19c
• Oracle Database SQL Tuning Guide, 19c