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Within the WSO2 platform, we use Tomcat JDBC pooling as the default pooling framework due to its production ready stability and high performance. The table below indicates some recommendations on how to configure the JDBC pool using the <DSS_HOME>/repository/conf/datasources/master-datasources.xml file. For more details about recommended JDBC configurations, see The Tomcat JDBC Connection Pool.

PropertyDescriptionRecommendationTuning Recommendations

The maximum number of active connections that can be allocated from the connection pool at the same time. The default value is 100.

This value should match the maximum number of requests that can be expected at a time in your production environment. This is to ensure that, whenever there is a sudden increase in the number of requests to the server, all of them can be connected successfully without causing any delays.

The maximum latency (approximately) = (P / M) * T ,


  • M = maxActive value
  • P = Peak concurrency value
  • T = Time (average) taken to process a query.

Therefore, by increasing the maxActive value (up to the expected highest number of concurrency), the time that requests wait in the queue for a connection to be released will decrease. But before increasing the Max. Active value, consult the database administrator, as it will create up to maxActive connections from a single node during peak times, and it may not be possible for the DBMS to handle the accumulated count of these active connections.

Note that this value should not exceed the maximum number of requests allowed for your database.

maxWaitThe maximum time that requests wait in the queue for a connection to be released.

Adjust this to a value slightly higher than the maximum latency for a request. That is, maxWait = (P / M) * T + buffer time.

minIdleThe minimum number of connections that can remain idle in the pool, without extra ones being created. The connection pool can shrink below this number if validation queries fail. Default value is 0.This value should be similar or near to the average number of requests that will be received by the server at the same time. With this setting, you can avoid having to open and close new connections every time a request is received by the server.
maxIdleThe maximum number of connections that can remain idle in the pool.The value should be less than the maxActive value. For high performance, tune maxIdle to match the number of average, concurrent requests to the pool. If this value is set to a large value, the pool will contain unnecessary idle connections.

The indication of whether connection objects will be validated before they are borrowed from the pool. If the object validation fails, it will be dropped from the pool, and we will attempt to borrow another connection.

Setting this property to 'true' is recommended as it will avoid connection requests from failing. The validationQuery property should be used if testOnBorrow is set to true. To increase the efficiency of connection validation and to improve performance, validationInterval property should also be used.


To avoid excess validation, run validation at most at this frequency (time in milliseconds). If a connection is due for validation, but has been validated previously within this interval, it will not be validated again. The default value is 30000 (30 seconds).

This time out can be as high as the time it takes for your DBMS to declare a connection as stale. For example, MySQL will keep a connection open for as long as 8 hours, which requires the validation interval to be within that range. However, note that having a low value for validation interval will not incur a big performance penalty, specially when database requests have a high throughput. For example, a single extra validation query run every 30 seconds is usually negligible.

validationQueryThe SQL query used to validate connections from this pool before returning them to the caller. If specified, this query does not have to return any data, it just can't throw an SQLException. The default value is null. Example values are SELECT 1(mysql), select 1 from dual(oracle), SELECT 1(MS Sql Server).Specify an SQL query, which will validate the availability of a connection in the pool. This query is necessary when testOnBorrow property is true.