In this scenario, DB2 will utilize the concurrency control mechanism to manage locks efficiently. When transaction T1 holds an exclusive lock on a row, transaction T2 requesting a shared lock will be blocked until T1 releases its lock. Therefore, T1 will be blocked until T2 releases the shared lock, which maintains data consistency and avoids the risk of concurrent updates. 

In Visual Explain, the thickness of an arrow between nodes indicates the strength of the relationship between the connected nodes. A thicker arrow signifies a stronger relationship, such as a larger amount of data being transferred or a more significant operation occurring between the nodes. Understanding the thickness of these arrows helps in visualizing the flow and impact of the query execution plan. 

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. 

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. 

The correct option is Option 1: Double-precision data. DOUBLE in DB2 represents a double-precision floating-point number, which is suitable for storing large numeric values with decimal points with high precision.