To automate the instantiation of a PDB in the standby database after creating a remote clone in the primary database, certain conditions must be met:
Open PDBI (remote clone source) in Read Only (A): The source PDB from which the clone is created must be open in read-only mode to ensure a consistent state during cloning.
Set STANDBY_PDB_SOURCE_FILE_DIRECTORY to <location of the PDB> in the london database (C): This parameter specifies the location on the standby database where the files from the source PDB should be placed.
Set STANDBY_FILE_MANAGEMENT to auto in the london database (F): This parameter automates the management of file changes on the standby database when structural changes occur on the primary database, ensuring that the clone operation is reflected automatically on the standby.
Reference:
Oracle Multitenant Administrator's Guide
Oracle Data Guard Broker documentation

A Physical Standby Database can indeed be converted into a Logical Standby Database, providing flexibility in a Data Guard configuration. This allows for the database to switch roles and supports SQL apply operations, enabling more granular control over the data and transactions being replicated and applied. Additionally, having a configuration with a primary database and one or more physical standby databases allows for rolling upgrades to be performed. This means that each database in the Data Guard configuration can be upgraded in a phased manner, minimizing downtime and ensuring high availability during the upgrade process.

In the context of Oracle Data Guard and Global Database Services (GDS):
* DGMGRL may be used to add the Sales configuration to the Prod pool in gds (A): Data Guard Broker's command-line interface DGMGRL can be utilized to manage configurations with GDS, allowing the addition of Data Guard Broker configurations to GDS pools.
* Performing a role change with DGMGRL automatically notifies GDS which in turn activates the appropriate services (B): When a role change is executed using DGMGRL, GDS is automatically notified, and it then activates the services that are appropriate for the new database roles.
* DGMGRL may be used to add a single database to the Sales configuration even if Sales is a member of the Prod pool (C): DGMGRL provides the capability to manage individual databases within a broker configuration, including adding databases to a configuration that is already part of a GDS pool.References:
* Oracle Data Guard Broker documentation
* Oracle Global Data Services documentation

C; The LGWR (Log Writer) process is responsible for writing redo entries from the redo log buffer to the online redo log files on the primary database. This is a fundamental process in the Oracle Database architecture, ensuring that all changes made to the database are captured for purposes such as recovery, replication, and high availability.
D; Real-time apply on a logical standby database requires standby redo log files. The standby redo log files are used to store redo data received from the primary database before it is applied to the logical standby database.
This enables the logical standby to apply changes as they are received, without waiting for the current redo log file to be archived.
E: Similarly, on a physical standby database, standby redo log files are used for real-time apply. They store redo data from the primary database, allowing the physical standby to apply redo data concurrently as it is received, rather than waiting for redo log files to be archived. This capability is crucial for maintaining a physical standby database that is closely synchronized with the primary database with minimal lag.
These functionalities are integral to Oracle Data Guard configurations and are not dependent on Oracle Streams or Oracle GoldenGate, which are separate technologies for data replication and integration.

The execution of the UNSKIP procedure is designed to remove SQL Apply filters that have been previously set up on a logical standby database. Based on the provided statements, the UNSKIP procedure is directed to delete any SQL Apply filters for DML statements associated with objects in the 'HR' schema that start with
'EMP'. Since both SKIP procedures had the same schema name ('HR') and statement type ('DML'), and the UNSKIP procedure uses a wildcard (%) for the object name, it will successfully remove both of the SQL Apply filters for 'EMP_NEW' and 'EMP_OLD', as both object names match the pattern provided in the UNSKIP procedure.
References:Oracle's Data Guard documentation and SQL Language Reference provide insights into managing SQL Apply filters on a logical standby database using the DBMS_LOGSTDBY package. This includes adding and removing filters through SKIP and UNSKIP procedures.