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## com.sleepycat.je
Class EnvironmentMutableConfig

    java.lang.Object
      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.

- `setTxnNoSync(boolean)`, `getTxnNoSync()`
- `setTxnWriteNoSync(boolean)`, `getTxnWriteNoSync()`

#### 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.

- je.maxMemory (`setCacheSize(long)`, `getCacheSize()`)
- je.maxMemoryPercent (`setCachePercent(int)`, `getCachePercent()`)
- je.env.runINCompressor
- je.env.runEvictor
- je.env.runCheckpointer
- je.env.runCleaner

#### 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 cache does not include transient objects created by the JE library, such as cursors, locks and transactions.

  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`

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