Database & JDBC Testing

Generate a JMeter JDBC test plan for database performance testing:

Database: [MySQL / PostgreSQL / Oracle / SQL Server]
JDBC URL: [jdbc:mysql://localhost:3306/testdb]
Driver class: [com.mysql.cj.jdbc.Driver]
Username/password: parameterized via CSV

Queries to test:
1. SELECT: [your query]
2. INSERT: [your query]
3. UPDATE: [your query]

Include:
- JDBC Connection Configuration element
- JDBC Request sampler for each query
- Result variable extraction for SELECT results
- Connection pool settings (maxActive, maxIdle, maxWait)
- Proper connection cleanup
- Full JMX XML output

During my load test, I'm seeing errors like:
"Cannot get a connection, pool error: Timeout waiting for connection"
OR
"HikariPool - Connection is not available, request timed out after Nms"

Diagnose and fix:
- What is connection pool exhaustion and why does it happen under load?
- How to calculate the right pool size for my workload
- HikariCP configuration best practices (minimumIdle, maximumPoolSize, connectionTimeout, idleTimeout)
- Spring Boot application.properties settings
- How to monitor connection pool in Grafana/Prometheus
- What to look for in slow query logs