The maximum number of active connections to the database that can be allocated from this data source at the same time. The default is 20.

Since there is a limited number of connections that applications can make to the database, this field prevents one connected system from using the entire connection pool. You can raise or lower this number to control the number of connection pools for a data source.

For example, if you have a data source for an application with low usage, you can lower this number to further limit the number of connection pools for the application. This would prevent the application from taking up too many resources.

The degree of isolation or concurrency control applied to transactions in a database system. This determines how transactions interact with each other and how they access and modify data concurrently. There are four transaction isolation levels available in the JDBC API. It's important to note that not all database vendors support all four levels.

• TRANSACTION_READ_UNCOMMITTED: This is the lowest isolation level where it allows dirty reads, non-repeatable reads, and phantom reads.
• TRANSACTION_READ_COMMITTED: A transaction can only read data that has been committed by other transactions. It prevents dirty reads. But non-repeatable reads and phantom reads can occur.
• TRANSACTION_REPEATABLE_READ: Ensures that within a transaction, the same query will always return the same results. This prevents dirty reads and non-repeatable reads. But phantom reads can still occur.
• TRANSACTION_SERIALIZABLE: This is the highest isolation level, providing strict data consistency. This ensures that concurrent transactions behave as if they are executed serially, preventing dirty reads, non-repeatable reads, and phantom reads.