The monitoring timer thread monitors JavaVM memory and sends a garbage collection execution request to garbage collection control functionality, if any of the following conditions are fulfilled:

• Tenured area consumption size / Tenured area total size x 100 = threshold of garbage collection control
• New area total size / Tenured area maximum free size x 100 = threshold of garbage collection control
• Permanent area consumption size / Permanent area total size x 100 = threshold of garbage collection control

When a garbage collection execution request is generated, the garbage collection control functionality checks connections used by the batch application. When checking the connections, the functionality confirms whether the batch application is performing resource exclusion.

The following table describes states considered as the resources are in exclusion.

Table 2-28 States considered as resource is under exclusion

Transaction	State		DB Connector	JDBC
Out of transaction	Executing SQL statement#1	When executing java.sql.Statement#execute When executing java.sql.Statement#executeUpdate When executing java.sql.Statement#executeQuery When executing java.sql.Statement#executeBatch	Y	N
	Performing operations for ResultSet	When executing java.sql.ResultSet#deleteRow When executing java.sql.ResultSet#insertRow When executing java.sql.ResultSet#updateRow	Y	N
	Performing operation such as object acquisition#1	When executing java.sql.Statement#addBatch When executing java.sql.Connection#prepareCall When executing java.sql.Connection#prepareStatement	Y	N
During transaction	When executing transaction with Connection API#2 When executing local transaction (JTA)#2.		Y	N
	When executing global transaction (JTA)		--	--

Legend: Y: Handled as resource under exclusion

N: Handled as resource not under exclusion

--: Not applicable

#1: java.sql.Statement in the table -includes sub-interfaces java.sql.PreparedStatement and java.sql.CallableStatement.

#2: Shows a status after starting a transaction (after executing setAutoCommit(false) or UserTransaction.begin), in which execution of SQL statement or operation for ResultSet is performed one or more times, and transaction conclusion processing is not complete.

Resource operations performed by using JDBC are handled as no resource exclusion. For example, if you execute a program in which execution of JDBC SQL statements and transaction processing on DB Connector are mixed, only the transaction processing on DB Connector is targeted for the garbage collection control functionality.

If it is determined that resources are in exclusion, the KDJE55024-I message is output and the state is waiting for execution of a full garbage collection. The full garbage collection continues to be in standby state even if there is single resource exclusion. The following figure shows an example of waiting for execution of the full garbage collection.

Figure 2-16 Example of waiting for execution of the full garbage collection

In this figure, two resources are accessed in a single job program. If execution of a full garbage collection is requested during resource exclusion, the garbage collection control functionality sets execution of the full garbage collection to standby state. When con2.commit() that ends the access of two resources is executed, the exclusion is removed.

If there is no resource exclusion, a full garbage collection is executed.

• You can concurrently execute only one batch application.
• You can execute processing to multiple resources from one batch application. However, you cannot use global transactions.
• If there is no sufficient free memory even in the state of waiting for execution of full garbage collection, JavaVM might perform full garbage collection. This occurs when a threshold of memory usage for executing garbage collection is large or when exclusion interval of resource is long. See 9.4 Setting threshold used in garbage collection control in the uCosminexus Application Server System Design Guide and tune the threshold of memory usage.