Reason for determining that option B is incorrect:
The PARALLEL=4 option specifies the parallel processing setting used in the Data Pump Export utility (expdp). This option sets the maximum number of active execution processes used for the export job.
In the command provided in the question, PARALLEL=4 is specified. This instructs Data Pump to attempt to use a maximum of 4 parallel processes (a combination of worker processes and parallel I/O server processes) to perform the export. However, this does not guarantee that 4 processes will be used. The actual number of processes used depends on available system resources and other constraints.
Explanation of option B:
The choice "It starts only when four worker processes are available" is incorrect. PARALLEL=4 requests Data Pump to use 4 parallel processes, but it does not delay the start of the job until 4 processes are available. The specified number of worker processes are allocated based on available resources.
According to the Oracle official reference, when PARALLEL=4 is specified, the behavior is as follows:
1. Data Pump attempts to use a maximum of 4 parallel processes (worker processes and parallel I/O server processes) to perform the export.
2. The actual number of processes used depends on system resources and other constraints.
3. Even if 4 processes are not available, the job starts with the number of processes that are available.
4. During job execution, the value of PARALLEL can be increased or decreased using interactive mode commands.
Therefore, PARALLEL=4 requests the use of 4 parallel processes, but it does not guarantee that 4 processes will be used, nor does it delay the start of the job until 4 processes are available.
2.6.5 Performing a Parallel Full Database Export
To learn how to perform a parallel full database export, use this example to understand the syntax.
This example shows a full database export that would use up to three parallel processes (worker or PQ worker processes) at any given time.
B - Oracle uses the MAX_DATAPUMP_PARALLEL_PER_JOB parameter to set the maximum number of parallel processes allowed per Oracle Data Pump job.
https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/MAX_DATAPUMP_PARALLEL_PER_JOB.html#GUID-33B1F962-B8C3-4DCE-BE68-66FC5D34ECA3
How to test it:
alter session set container=cdb$root;
alter system set max_datapump_parallel_per_job=2 scope=both;
If you try to start a job with PARALLEL=4 Oracle will return an error:
ORA-31626: job does not exist
ORA-31637: cannot create job EXPFULL for user SYSTEM
D - Is wrong because "Several system schemas cannot be exported, because they are not user schemas; they contain Oracle-managed data and metadata. Examples of schemas that are not exported include SYS, ORDSYS, and MDSYS."
https://docs.oracle.com/en/database/oracle/oracle-database/19/sutil/oracle-data-pump-export-utility.html#GUID-FCB1FA15-5798-48C0-85ED-08E9DAC5E687
D is correct:
"You can use Data Pump to carry out a full database export by using the FULL parameter.
In a full database export, the ENTIRE DATABASE is unloaded. This mode requires that you have the DATAPUMP_EXP_FULL_DATABASE role."
https://docs.oracle.com/en/database/oracle/oracle-database/19/sutil/oracle-data-pump-
export-utility.html#GUID-079769D8-40F4-432F-88AD-E7264D7A2E2D
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