The performance impact of data compression in DB2 varies depending on several factors, including the characteristics of the data being compressed, the compression ratio achieved, and the overall size of the database. Additionally, the hardware configuration of the system can also influence the performance impact of data compression. 

The UPDATE statement in SQL is used to modify existing records in a table. It allows users to change the values of one or more columns in existing rows based on specified conditions. This statement is crucial for updating data in a database when there are changes or corrections needed in the existing records. 

SYSIBM.SNAPDB is a system table that provides a snapshot of database health, including information about locks, buffer pool usage, and other vital statistics. Querying this table can help DBAs monitor and maintain the health of their DB2 databases. 

Before running the Reorg utility, it's essential to consider factors such as the size of the database, current workload, available disk space, and memory to ensure efficient execution. 

The unique constraint in DB2 ensures that each value in a column is unique and does not allow duplicate values. This constraint is often used to enforce entity integrity by ensuring that no two rows in a table have the same value for a specified column or combination of columns. 

DB2 uses a deadlock detection algorithm that detects when two or more transactions are waiting for locks held by each other, and it resolves these deadlocks by rolling back one of the transactions involved. Deadlocks are detected by DB2 automatically. 

Optimizing the execution of Runstats and Reorg utilities in DB2 involves various strategies aimed at minimizing downtime and maximizing efficiency. These include scheduling these utilities during off-peak hours to reduce the impact on production systems, allocating adequate system resources for faster execution, utilizing utility options like SAMPLED or DELTA to reduce overhead, and parallelizing Reorg tasks across multiple CPUs to expedite the process. Implementing these strategies can significantly enhance the performance and reliability of DB2 databases. 

Triggers in DB2 are powerful tools used to enforce business rules, perform data validation, and maintain data consistency. They allow users to define actions that automatically execute when specified database events occur, such as INSERT, UPDATE, or DELETE operations. This ensures that data integrity is maintained by enforcing predefined rules and actions, such as checking constraints, cascading updates, or auditing changes. 

The key difference between a sensitive and an insensitive cursor in DB2 lies in how they react to changes made to the underlying data. A sensitive cursor reflects all changes made to the data, ensuring that any updates, inserts, or deletes performed by other transactions are visible to the cursor. On the other hand, an insensitive cursor does not reflect such changes and presents a consistent view of the data as it was when the cursor was opened. Sensitive cursors are useful in applications where real-time data updates are essential, while insensitive cursors may be preferred for performance reasons or when data consistency is not critical. 

The main role of an index in a database is to improve query performance by facilitating rapid data retrieval. An index is a data structure that contains keys derived from one or more columns of a table, allowing the database management system to locate specific rows efficiently. By reducing the number of disk accesses needed to fulfill queries, indexes speed up data retrieval operations and enhance overall system performance.