ちなみに、Tomcatはデータベース接続の管理とは何の関係もありません。 Grails2.3.6 以降 、これらは推奨されるデフォルトのデータソースプロパティです:
properties {
//see http://grails.org/doc/latest/guide/conf.html#dataSource for documentation
jmxEnabled = true
initialSize = 5
maxActive = 50
minIdle = 5
maxIdle = 25
maxWait = 10000
maxAge = 10 * 60000
timeBetweenEvictionRunsMillis = 5000
minEvictableIdleTimeMillis = 60000
validationQuery = "SELECT 1"
validationQueryTimeout = 3
validationInterval = 15000
testOnBorrow = true
testWhileIdle = true
testOnReturn = false
jdbcInterceptors = "ConnectionState;StatementCache(max=200)"
defaultTransactionIsolation = java.sql.Connection.TRANSACTION_READ_COMMITTED
}