Stored procedures in DB2 serve primarily to encapsulate and centralize business logic. They allow developers to define sets of SQL statements as a single unit, which can then be executed multiple times without the need to recompile the SQL code. This enhances code reusability, reduces network traffic, and improves overall application performance. 

Several factors should be considered when deciding whether to create an index on a column in DB2. These include the selectivity of the column, which determines how unique the values are, the frequency of data retrieval using the column, and the overall performance requirements of the system. Indexes should be created on columns that are frequently used in WHERE clauses and join conditions, but not on columns that have low selectivity or are rarely used in queries. 

Point-in-time recovery in DB2 refers to the process of restoring the database to a specific point in time, typically to recover from errors or data corruption. It involves rolling forward transactions to the desired point and then rolling back any uncommitted transactions, ensuring the database is consistent with its state at that specific time. 

An ERD (Entity-Relationship Diagram) aids in visualizing the structure of a database, showing entities, their attributes, and the relationships between them. It helps in understanding the database schema and designing the database efficiently. 

Reviewing installation logs is essential to identify the cause of the error. Installation logs typically contain detailed information about the installation process, including any errors encountered. This helps the DBA pinpoint the issue and take appropriate corrective actions. Checking system requirements and compatibility is crucial before starting the installation process, but it might not directly address the encountered error. Restarting the server or checking disk space availability are general troubleshooting steps and might not specifically address the installation error. 

The RESTORE command in DB2 is used to recover a database from a backup. It allows database administrators to restore the database to a previous state by applying the data stored in backup files. This command is essential in scenarios where data loss or corruption has occurred, enabling organizations to recover their databases and maintain business continuity. 

Performance tuning involves adjusting various database parameters to achieve optimal performance, such as buffer pool size, memory allocation, and query optimization. 

The Runstats utility in DB2 collects statistics about various database objects such as tables, indexes, columns, and partitions. These statistics help the query optimizer to make informed decisions about the most efficient way to access data, leading to improved query performance. 

The JSON_TABLE function in DB2 allows for querying and manipulating JSON data directly. It provides a way to extract data from JSON documents and transform it into relational format, facilitating seamless integration of JSON data with traditional SQL queries. 

Achieving BCNF helps in minimizing data redundancy and anomalies, thus improving data integrity. It ensures that every determinant is a candidate key, enhancing data integrity. BCNF may simplify data retrieval but does not directly impact query performance.