configure a pooled datasource and you can define how many connections the pool can contain.

Add min-pool-size and max-pool-size entries to your *-ds.xml file:

<datasources>
 <local-tx-datasource>
 ...
 <min-pool-size>5</min-pool-size>
 <max-pool-size>20</max-pool-size>
 <idle-timeout-minutes>5</idle-timeout-minutes>
 </local-tx-datasource>
</datasources>

Oh, and make sure that your database is configured to accept the same number of connections. If you have multiple data sources going to the same database, then the database max connections must be the sum of the max-pool-size values for all of the data sources.