The primary function of DB2 Control Center is database monitoring and performance tuning. It provides tools for administrators to monitor database activity, analyze performance metrics, and tune the database for optimal performance. With this tool, administrators can identify bottlenecks, optimize queries, and ensure smooth database operation. 

Control Center provides centralized management of DB2 instances and databases, allowing administrators to perform various tasks such as monitoring, configuring, and troubleshooting from a single interface. This centralized approach enhances efficiency and simplifies administration processes. 

The Database Services component in DB2 handles crucial functions such as concurrency control, ensuring transactions' atomicity, consistency, isolation, and durability (ACID properties), and manages data integrity through various mechanisms like constraints. 

Performing a comprehensive assessment of the existing DB2 environment is crucial to understand dependencies, constraints, and potential challenges, ensuring a smoother migration process. Rushing into migration without assessment or testing can lead to unexpected issues and downtime. 

Partitioning in DB2 serves the purpose of distributing data across multiple nodes in a distributed environment. This helps in achieving parallel processing and improving scalability by allowing workload to be distributed. 

The Reorg utility in DB2 is used to reorganize fragmented database objects such as tables and indexes. It helps to reclaim unused space, improve data access performance, and optimize storage utilization. During the reorganization process, the utility physically reorganizes the data pages, indexes, and other objects, resulting in a more compact and efficient storage layout. 

In DB2, the closing tag signifies the end of a tag scope. Tags in DB2 are typically used to group related database objects together, and the closing tag delineates the boundary of this grouping. Any objects defined within the tag are considered to be within its scope until the closing tag is encountered. This allows for the precise organization and management of database resources within the specified tag. 

Data distribution in a partitioned database environment is managed by partitions. In a partitioned database, data is distributed across multiple partitions, each containing a subset of the data. This distribution helps in achieving scalability, parallelism, and efficient data management in large-scale database environments. 

Database backup in DB2 is primarily performed to ensure data integrity. By creating regular backups, organizations can safeguard their data against unexpected events such as hardware failures, software errors, or data corruption. These backups provide a means to restore the database to a consistent state in case of any unforeseen circumstances, thereby maintaining data integrity. 

The compression dictionary in DB2 is primarily used for data compression. It helps in reducing storage requirements by storing frequently occurring data values only once, thus saving space. This dictionary is utilized during compression and decompression operations, aiding in efficient data storage and retrieval.