Berkeley DB Java Edition
version 3.3.75

com.sleepycat.je
Class EnvironmentMutableConfig

java.lang.Object
  extended by com.sleepycat.je.EnvironmentMutableConfig
All Implemented Interfaces:
Cloneable
Direct Known Subclasses:
EnvironmentConfig

public class EnvironmentMutableConfig
extends Object
implements Cloneable

Specifies the environment attributes that may be changed after the environment has been opened. EnvironmentMutableConfig is a parameter to Environment.setMutableConfig(com.sleepycat.je.EnvironmentMutableConfig) and is returned by Environment.getMutableConfig().

There are two types of mutable environment properties: per-environment handle properties, and environment wide properties.

Per-Environment Handle Properties

Per-environment handle properties apply only to a single Environment instance. For example, to change the default transaction commit behavior for a single environment handle, do this:

     // Specify no-sync behavior for a given handle.
     EnvironmentMutableConfig mutableConfig = myEnvHandle.getMutableConfig();
     mutableConfig.setTxnNoSync(true);
     myEnvHandle.setMutableConfig(mutableConfig);
 

The per-environment handle properties are listed below. These properties are accessed using the setter and getter methods listed, as shown in the example above.

Environment-Wide Mutable Properties

Environment-wide mutable properties are those that can be changed for an environment as a whole, irrespective of which environment instance (for the same physical environment) is used. For example, to stop the cleaner daemon thread, do this:

     // Stop the cleaner daemon thread for the environment.
     EnvironmentMutableConfig mutableConfig = myEnvHandle.getMutableConfig();
     mutableConfig.setConfigParam("je.env.runCleaner", "false");
     myEnvHandle.setMutableConfig(mutableConfig);
 

The environment-wide mutable properties are listed below. These properties are accessed using the setConfigParam(java.lang.String, java.lang.String) and getConfigParam(java.lang.String) methods, as shown in the example above, using the property names listed below. In some cases setter and getter methods are also available.

Getting the Current Environment Properties

To get the current "live" properties of an environment after constructing it or changing its properties, you must call Environment.getConfig() or Environment.getMutableConfig(). The original EnvironmentConfig or EnvironmentMutableConfig object used to set the properties is not kept up to date as properties are changed, and does not reflect property validation or properties that are computed. @see EnvironmentConfig


Constructor Summary
EnvironmentMutableConfig()
          An instance created using the default constructor is initialized with the system's default settings.
 
Method Summary
 int getCachePercent()
          Returns the percentage value used in the JE cache size calculation.
 long getCacheSize()
          Returns the memory available to the database system, in bytes.
 String getConfigParam(String paramName)
          Returns the value for this configuration parameter.
 ExceptionListener getExceptionListener()
          Returns the exception listener, if set.
 int getNumExplicitlySetParams()
          Testing support
 boolean getTxnNoSync()
          Returns true if the database environment is configured for asynchronous transactions.
 boolean getTxnWriteNoSync()
          Returns true if the database environment is configured for transactions which write but do not flush the log.
 void setCachePercent(int percent)
          By default, JE sets its cache size proportionally to the JVM memory.
 void setCacheSize(long totalBytes)
          Configures the memory available to the database system, in bytes.
 void setConfigParam(String paramName, String value)
          Validates the value prescribed for the configuration parameter; if it is valid, the value is set in the configuration.
 void setExceptionListener(ExceptionListener exceptionListener)
          Sets the exception listener for an Environment.
 void setTxnNoSync(boolean noSync)
          Configures the database environment for asynchronous transactions.
 void setTxnWriteNoSync(boolean writeNoSync)
          Configures the database environment for transactions which write but do not flush the log.
 String toString()
          Display configuration values.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

EnvironmentMutableConfig

public EnvironmentMutableConfig()
An instance created using the default constructor is initialized with the system's default settings.

Method Detail

setTxnNoSync

public void setTxnNoSync(boolean noSync)
Configures the database environment for asynchronous transactions.

Parameters:
noSync - If true, do not write or synchronously flush the log on transaction commit. This means that transactions exhibit the ACI (Atomicity, Consistency, and Isolation) properties, but not D (Durability); that is, database integrity is maintained, but if the JVM or operating system fails, it is possible some number of the most recently committed transactions may be undone during recovery. The number of transactions at risk is governed by how many updates fit into a log buffer, how often the operating system flushes dirty buffers to disk, and how often the database environment is checkpointed.

This attribute is false by default for this class and for the database environment.

Throws:
DatabaseException - if a failure occurs.

getTxnNoSync

public boolean getTxnNoSync()
Returns true if the database environment is configured for asynchronous transactions.

Returns:
true if the database environment is configured for asynchronous transactions.

setTxnWriteNoSync

public void setTxnWriteNoSync(boolean writeNoSync)
Configures the database environment for transactions which write but do not flush the log.

Parameters:
writeNoSync - If true, write but do not synchronously flush the log on transaction commit. This means that transactions exhibit the ACI (Atomicity, Consistency, and Isolation) properties, but not D (Durability); that is, database integrity is maintained, but if the operating system fails, it is possible some number of the most recently committed transactions may be undone during recovery. The number of transactions at risk is governed by how often the operating system flushes dirty buffers to disk, and how often the database environment is checkpointed.

The motivation for this attribute is to provide a transaction that has more durability than asynchronous (nosync) transactions, but has higher performance than synchronous transactions.

This attribute is false by default for this class and for the database environment.

Throws:
DatabaseException - if a failure occurs.

getTxnWriteNoSync

public boolean getTxnWriteNoSync()
Returns true if the database environment is configured for transactions which write but do not flush the log.

Returns:
true if the database environment is configured for transactions which write but do not flush the log.

setCacheSize

public void setCacheSize(long totalBytes)
                  throws IllegalArgumentException
Configures the memory available to the database system, in bytes.

Equivalent to setting the je.maxMemory property in the je.properties file. The system will evict database objects when it comes within a prescribed margin of the limit.

By default, JE sets the cache size to:

je.maxMemoryPercent * JVM maximum memory

where JVM maximum memory is specified by the JVM -Xmx flag. However, calling setCacheSize() with a non-zero value overrides the percentage based calculation and sets the cache size explicitly.

Note that the log buffer cache may be cleared if the cache size is changed after the environment has been opened.

If setSharedCache(true) is called, setCacheSize and setCachePercent specify the total size of the shared cache, and changing these parameters will change the size of the shared cache.

Parameters:
totalBytes - The memory available to the database system, in bytes.
Throws:
IllegalArgumentException - if an invalid parameter was specified.
DatabaseException - if a failure occurs.

getCacheSize

public long getCacheSize()
Returns the memory available to the database system, in bytes. A valid value is only available if this EnvironmentConfig object has been returned from Environment.getConfig();

Returns:
The memory available to the database system, in bytes.

setCachePercent

public void setCachePercent(int percent)
                     throws IllegalArgumentException

By default, JE sets its cache size proportionally to the JVM memory. This formula is used:

         je.maxMemoryPercent *  JVM maximum memory
 

where JVM maximum memory is specified by the JVM -Xmx flag. setCachePercent() specifies the percentage used and is equivalent to setting the je.maxMemoryPercent property in the je.properties file.

Calling setCacheSize() with a non-zero value overrides the percentage based calculation and sets the cache size explicitly.

Note that the log buffer cache may be cleared if the cache size is changed after the environment has been opened.

If setSharedCache(true) is called, setCacheSize and setCachePercent specify the total size of the shared cache, and changing these parameters will change the size of the shared cache.

Parameters:
percent - The percent of JVM memory to allocate to the JE cache.
Throws:
IllegalArgumentException - if an invalid parameter was specified.
DatabaseException - if a failure occurs.

getCachePercent

public int getCachePercent()
Returns the percentage value used in the JE cache size calculation.

Returns:
the percentage value used in the JE cache size calculation.

setExceptionListener

public void setExceptionListener(ExceptionListener exceptionListener)
Sets the exception listener for an Environment. The listener is called when a daemon thread throws an exception, in order to provide a notification mechanism for these otherwise asynchronous exceptions. Daemon thread exceptions are also printed through stderr.

Not all daemon exceptions are fatal, and the application bears responsibility for choosing how to respond to the notification. Since exceptions may repeat, the application should also choose how to handle a spate of exceptions. For example, the application may choose to act upon each notification, or it may choose to batch up its responses by implementing the listener so it stores exceptions, and only acts when a certain number have been received.

Parameters:
exceptionListener - the callback to be executed when an exception occurs.

getExceptionListener

public ExceptionListener getExceptionListener()
Returns the exception listener, if set.


setConfigParam

public void setConfigParam(String paramName,
                           String value)
                    throws IllegalArgumentException
Validates the value prescribed for the configuration parameter; if it is valid, the value is set in the configuration.

Parameters:
paramName - The name of the configuration parameter. See the sample je.properties file for descriptions of all parameters.
value - The value for this configuration parameter.
Throws:
IllegalArgumentException - if an invalid parameter was specified.
DatabaseException - if a failure occurs.

getConfigParam

public String getConfigParam(String paramName)
                      throws IllegalArgumentException
Returns the value for this configuration parameter.

Parameters:
paramName - Name of the requested parameter.
Throws:
IllegalArgumentException - if the configParamName is invalid.

getNumExplicitlySetParams

public int getNumExplicitlySetParams()
Testing support


toString

public String toString()
Display configuration values.

Overrides:
toString in class Object

Berkeley DB Java Edition
version 3.3.75

Copyright (c) 2004,2008 Oracle. All rights reserved.