Performance tuning in DB2 can improve various operations such as data retrieval by optimizing SQL queries, creating appropriate indexes, and configuring memory settings to enhance overall system performance. 

Third-party command line tools may offer specialized features for performance tuning tasks in DB2 administration. These tools often provide advanced performance analysis, optimization, and tuning capabilities to enhance the overall performance and efficiency of DB2 databases and applications. 

DB2 implements optimistic concurrency control through MVCC (Multi-Version Concurrency Control). This mechanism allows transactions to proceed without waiting for others to complete, by maintaining multiple versions of a data item. When a transaction reads a data item, it gets a timestamp, and if another transaction updates the same data after that timestamp, the database creates a new version of the data, maintaining the older version for read consistency. MVCC reduces contention and improves concurrency in DB2 systems. 

The LOAD utility in DB2 is used to insert large volumes of data efficiently into database tables. It is particularly useful when dealing with massive data loads, such as during initial database population or data warehousing operations. The LOAD utility bypasses much of the normal processing done during INSERT operations, resulting in faster data loading. 

DB2 manages encryption keys for encrypted data by using a key management system to securely store and distribute encryption keys. This ensures that only authorized users can access encrypted data securely. 

Indexes in DB2 improve query performance. They serve as a data structure that helps in quickly locating and accessing specific rows within a table based on the indexed columns. By creating indexes on columns frequently used in search criteria or join conditions, DB2 can efficiently retrieve data, leading to faster query execution times and overall improved system performance. 

Encryption in DB2 ensures the confidentiality of data, meaning that even if unauthorized users gain access to the data, they won't be able to understand or decipher it without the proper decryption keys. This ensures that sensitive information remains protected from unauthorized access or viewing. 

In a Visual Explain diagram, a node represents a step in the query execution plan. Each node corresponds to an operation performed during query execution, such as scanning a table or performing a join. Understanding the meaning of each node helps in analyzing and optimizing the query execution plan. 

Transparent Data Encryption (TDE) is a feature in DB2 that encrypts data at rest, providing protection against unauthorized access to sensitive information stored in the database files. It ensures that data remains encrypted even if the physical media is stolen or compromised. Other options mentioned may provide encryption in transit or custom encryption, but TDE specifically addresses data encryption at rest within the DB2 database. 

The utility commonly used for creating backups in DB2 is the BACKUP utility. This utility allows users to back up entire databases or specific tablespaces, ensuring that data can be restored in case of data loss or corruption. It provides options for full or incremental backups, as well as for specifying backup locations and formats.