XML and JSON support in DB2 enables seamless integration with web services and applications, allowing for the exchange of data in widely-used formats over the internet. This integration facilitates interoperability between different systems and platforms, enhancing the flexibility and accessibility of data stored in DB2 databases. 

When designing a disaster recovery plan for a mission-critical DB2 database, several factors must be considered, including the recovery time objective (RTO) and recovery point objective (RPO), which define the acceptable downtime and data loss respectively. Additionally, the plan should outline data replication methods such as HADR or log shipping to ensure data redundancy and minimize data loss. Regular failover testing should be conducted to validate the effectiveness of the plan and identify any potential weaknesses that need to be addressed. 

Monitoring in DB2 involves the continuous observation of various database performance metrics such as CPU usage, memory usage, I/O operations, and response times. This helps administrators identify potential bottlenecks or issues affecting the overall performance of the database system. 

In a self-join, a table is joined with itself based on a common column, allowing comparisons between rows within the same table. This is useful for hierarchical data or when comparing related records. 

Data compression in DB2 primarily aims to reduce storage space by compressing data, leading to efficient storage management and cost savings. It allows for storing more data in less space without compromising data integrity or accessibility. This can significantly benefit organizations dealing with large volumes of data by optimizing storage resources and enhancing overall system performance. 

The version number of DB2 signifies the release level of the software. It indicates the specific version or release of DB2, which includes enhancements, bug fixes, and new features introduced by IBM. For instance, version 11.5 denotes a different release than version 11.1, with each release potentially offering improvements and new functionalities. Database administrators need to be aware of the version number to ensure compatibility with their existing systems and to leverage the latest features available. 

Buffer pool tuning in DB2 involves adjusting the sizes and configurations of buffer pools, which are memory areas used to cache frequently accessed data. Proper buffer pool tuning can significantly improve performance by reducing the need for disk I/O operations, as data can be retrieved from memory more quickly. This can lead to lower CPU consumption and better overall response times for database queries and transactions. 

Different editions of DB2 are tailored to meet the diverse requirements of enterprises. These editions cater to varying needs such as the size of the organization, the complexity of workloads, and budget constraints. For instance, the Express edition targets small businesses with its cost-effective features, while the Enterprise edition is designed for large-scale deployments requiring robust performance and scalability. Understanding these editions helps organizations align their database solutions with their specific business objectives. 

To restore a critical table accidentally deleted in DB2, the DBA can perform a table-level restore from the last backup and apply transaction logs to recover data up to the point of deletion. This strategy helps minimize data loss by selectively restoring only the affected table without affecting the rest of the database. 

High availability setups aim to minimize downtime in case of system failure. Downtime refers to the period when a system is unavailable or inaccessible, which can result in significant losses for businesses.