com.sleepycat.db.Environment
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Berkeley DB version 4.4.20 |
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java.lang.Object
A database environment. Environments include support for some or all of caching, locking, logging and transactions.
To open an existing environment with default attributes the application may use a default environment configuration object or null:
// Open an environment handle with default attributes.
Environment env = new Environment(home, new EnvironmentConfig());
or
Environment env = new Environment(home, null);
Note that many Environment objects may access a single environment.
To create an environment or customize attributes, the application should customize the configuration class. For example:
EnvironmentConfig envConfig = new EnvironmentConfig();
envConfig.setTransactional(true);
envConfig.setAllowCreate(true);
envConfig.setCacheSize(1000000);
Environment newlyCreatedEnv = new Environment(home, envConfig);
Environment handles are free-threaded unless EnvironmentConfig.setThreaded is called to disable this before the environment is opened.
An environment handle is an Environment instance. More than one Environment instance may be created for the same physical directory, which is the same as saying that more than one Environment handle may be open at one time for a given environment.
The Environment handle should not be closed while any other handle
remains open that is using it as a reference (for example,
Database or Transaction. Once Environment.close
is called, this object may not be accessed again, regardless of
whether or not it throws an exception.
| Constructor Summary | |
Environment(File envHome,
EnvironmentConfig envConfig)
Create a database environment handle. |
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| Method Summary | |
Transaction |
beginTransaction(Transaction parent,
TransactionConfig txnConfig)
Create a new transaction in the database environment. |
void |
checkpoint(CheckpointConfig checkpointConfig)
Synchronously checkpoint the database environment. |
void |
close()
Close the database environment, freeing any allocated resources and closing any underlying subsystems. |
int |
createLockerID()
Allocate a locker ID. |
int |
detectDeadlocks(LockDetectMode mode)
Run one iteration of the deadlock detector. |
int |
electReplicationMaster(int nsites,
int nvotes,
int priority,
int timeout)
Hold an election for the master of a replication group. |
void |
freeLockerID(int id)
Free a locker ID. |
File[] |
getArchiveDatabases()
Return the names of the database files that need to be archived in order to recover the database from catastrophic failure. |
File[] |
getArchiveLogFiles(boolean includeInUse)
Return the names of all of the log files that are no longer in use. |
CacheFileStats[] |
getCacheFileStats(StatsConfig config)
Return the database environment's per-file memory pool (that is, the buffer cache) statistics. |
CacheStats |
getCacheStats(StatsConfig config)
|
EnvironmentConfig |
getConfig()
Return this object's configuration. |
File |
getHome()
Return the database environment's home directory. |
Lock |
getLock(int locker,
boolean noWait,
DatabaseEntry object,
LockRequestMode mode)
Acquire a lock from the lock table. |
LockStats |
getLockStats(StatsConfig config)
Return the database environment's locking statistics. |
String |
getLogFileName(LogSequenceNumber lsn)
Return the name of the log file that contains the log record specified by a LogSequenceNumber object. |
LogStats |
getLogStats(StatsConfig config)
Return the database environment's logging statistics. |
MutexStats |
getMutexStats(StatsConfig config)
Return the database environment's mutex statistics. |
boolean |
getReplicationConfig(ReplicationConfig config)
Get the configuration of the replication subsystem. |
ReplicationStats |
getReplicationStats(StatsConfig config)
Return the database environment's replication statistics. |
TransactionStats |
getTransactionStats(StatsConfig config)
Return the database environment's transactional statistics. |
static int |
getVersionMajor()
Return the release major number. |
static int |
getVersionMinor()
Return the release minor number. |
static int |
getVersionPatch()
Return the release patch number. |
static String |
getVersionString()
Return the release version information, suitable for display. |
void |
lockVector(int locker,
boolean noWait,
LockRequest[] list)
Atomically obtain and release one or more locks from the lock table. |
void |
logFlush(LogSequenceNumber lsn)
Flush log records to stable storage. |
void |
logPrint(Transaction txn,
String message)
Append an informational message to the Berkeley DB database environment log files. |
LogSequenceNumber |
logPut(DatabaseEntry data,
boolean flush)
Append a record to the log. |
Database |
openDatabase(Transaction txn,
String fileName,
String databaseName,
DatabaseConfig config)
Open a database. |
LogCursor |
openLogCursor()
Return a log cursor. |
SecondaryDatabase |
openSecondaryDatabase(Transaction txn,
String fileName,
String databaseName,
Database primaryDatabase,
SecondaryConfig config)
Open a database. |
void |
panic(boolean onoff)
Set the panic state for the database environment. |
ReplicationStatus |
processReplicationMessage(DatabaseEntry control,
DatabaseEntry rec,
int envid)
Process an incoming replication message sent by a member of the replication group to the local database environment. |
void |
putLock(Lock lock)
Release a lock. |
PreparedTransaction[] |
recover(int count,
boolean continued)
Return a list of prepared but not yet resolved transactions. |
static void |
remove(File home,
boolean force,
EnvironmentConfig config)
Destroy a database environment. |
void |
removeDatabase(Transaction txn,
String fileName,
String databaseName)
Remove a database. |
void |
removeOldLogFiles()
Remove log files that are no longer needed. |
void |
renameDatabase(Transaction txn,
String fileName,
String oldDatabaseName,
String newDatabaseName)
Rename a database. |
void |
setConfig(EnvironmentConfig config)
Change the settings in an existing environment handle. |
void |
setReplicationConfig(ReplicationConfig config,
boolean onoff)
Configure the replication subsystem. |
void |
startReplication(DatabaseEntry cdata,
boolean master)
Configure the database environment as a client or master in a group of replicated database environments. |
void |
syncReplication()
Forces synchronization to begin for this client. |
int |
trickleCacheWrite(int percent)
Ensure that a specified percent of the pages in the shared memory pool are clean, by writing dirty pages to their backing files. |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
public Environment(File envHome,
EnvironmentConfig envConfig)
throws DatabaseException,
FileNotFoundException
envHome - The database environment's home directory.
The environment variable DB_HOME may be used as
the path of the database home.
For more information on envHome and filename
resolution in general, see
File Naming.
envConfig - The database environment attributes. If null, default attributes are used.
IllegalArgumentException - if an invalid parameter was specified.
DatabaseException - if a failure occurs.
FileNotFoundException| Method Detail |
public File getHome()
throws DatabaseException
DatabaseException - if a failure occurs.
public EnvironmentConfig getConfig()
throws DatabaseException
DatabaseException - if a failure occurs.
public Transaction beginTransaction(Transaction parent,
TransactionConfig txnConfig)
throws DatabaseException
Transactions may only span threads if they do so serially; that is, each transaction must be active in only a single thread of control at a time.
This restriction holds for parents of nested transactions as well; no two children may be concurrently active in more than one thread of control at any one time.
Cursors may not span transactions; that is, each cursor must be opened and closed within a single transaction.
A parent transaction may not issue any Berkeley DB operations --
except for Environment.beginTransaction,
Transaction.abort and Transaction.commit --
while it has active child transactions (child transactions that have
not yet been committed or aborted).
parent - If the parent parameter is non-null, the new transaction will be a
nested transaction, with the transaction indicated by parent as its
parent. Transactions may be nested to any level. In the presence
of distributed transactions and two-phase commit, only the parental
transaction, that is a transaction without a parent specified,
should be passed as an parameter to Transaction.prepare.
txnConfig - The transaction attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public void checkpoint(CheckpointConfig checkpointConfig)
throws DatabaseException
checkpointConfig - The checkpoint attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public LockStats getLockStats(StatsConfig config)
throws DatabaseException
config - The locking statistics attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public TransactionStats getTransactionStats(StatsConfig config)
throws DatabaseException
config - The transactional statistics attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public void close()
throws DatabaseException
The Environment handle should not be closed while any other
handle that refers to it is not yet closed; for example, database
environment handles must not be closed while database handles remain
open, or transactions in the environment have not yet been committed
or aborted. Specifically, this includes Database,
Cursor, Transaction, and LogCursor
handles.
Where the environment was initialized with a locking subsystem, closing the environment does not release any locks still held by the closing process, providing functionality for long-lived locks.
Where the environment was initialized with a transaction subsystem, closing the environment aborts any unresolved transactions. Applications should not depend on this behavior for transactions involving databases; all such transactions should be explicitly resolved. The problem with depending on this semantic is that aborting an unresolved transaction involving database operations requires a database handle. Because the database handles should have been closed before closing the environment, it will not be possible to abort the transaction, and recovery will have to be run on the database environment before further operations are done.
Where log cursors were created, closing the environment does not imply closing those cursors.
In multithreaded applications, only a single thread may call this method.
After this method has been called, regardless of its return, the
Environment handle may not be accessed again.
DatabaseException - if a failure occurs.
public static void remove(File home,
boolean force,
EnvironmentConfig config)
throws DatabaseException,
FileNotFoundException
If the environment is not in use, the environment regions, including any backing files, are removed. Any log or database files and the environment directory itself are not removed.
If there are processes currently using the database environment, this method will fail without further action (unless the force argument is true, in which case the environment will be removed, regardless of any processes still using it).
The result of attempting to forcibly destroy the environment when it is in use is unspecified. Processes using an environment often maintain open file descriptors for shared regions within it. On UNIX systems, the environment removal will usually succeed, and processes that have already joined the region will continue to run in that region without change. However, processes attempting to join the environment will either fail or create new regions. On other systems in which the unlink system call will fail if any process has an open file descriptor for the file (for example Windows/NT), the region removal will fail.
Calling this method should not be necessary for most applications because the environment is cleaned up as part of normal database recovery procedures. However, applications may want to call this method as part of application shut down to free up system resources. For example, if system shared memory was used to back the database environment, it may be useful to call this method in order to release system shared memory segments that have been allocated. Or, on architectures in which mutexes require allocation of underlying system resources, it may be useful to call this method in order to release those resources. Alternatively, if recovery is not required because no database state is maintained across failures, and no system resources need to be released, it is possible to clean up an environment by simply removing all the Berkeley DB files in the database environment's directories.
In multithreaded applications, only a single thread may call this method.
After this method has been called, regardless of its return, the
Environment handle may not be accessed again.
home - The database environment to be removed.
On Windows platforms, this argument will be interpreted as a UTF-8
string, which is equivalent to ASCII for Latin characters.
force - The environment is removed, regardless of any processes that may
still using it, and no locks are acquired during this process.
(Generally, the force argument is specified only when applications
were unable to shut down cleanly, and there is a risk that an
application may have died holding a Berkeley DB mutex or lock.
DatabaseException - if a failure occurs.
FileNotFoundException
public void setConfig(EnvironmentConfig config)
throws DatabaseException
config - The database environment attributes. If null, default attributes are used.
IllegalArgumentException - if an invalid parameter was specified.
DatabaseException - if a failure occurs.
public Database openDatabase(Transaction txn,
String fileName,
String databaseName,
DatabaseConfig config)
throws DatabaseException,
FileNotFoundException
The database is represented by the file and database parameters.
The currently supported database file formats (or access methods) are Btree, Hash, Queue, and Recno. The Btree format is a representation of a sorted, balanced tree structure. The Hash format is an extensible, dynamic hashing scheme. The Queue format supports fast access to fixed-length records accessed sequentially or by logical record number. The Recno format supports fixed- or variable-length records, accessed sequentially or by logical record number, and optionally backed by a flat text file.
Storage and retrieval are based on key/data pairs; see DatabaseEntry
for more information.
Opening a database is a relatively expensive operation, and maintaining a set of open databases will normally be preferable to repeatedly opening and closing the database for each new query.
In-memory databases never intended to be preserved on disk may be
created by setting both the fileName and databaseName parameters to
null. Note that in-memory databases can only ever be shared by sharing
the single database handle that created them, in circumstances where
doing so is safe. The environment variable TMPDIR may
be used as a directory in which to create temporary backing files.
txn - For a transactional database, an explicit transaction may be specified, or null
may be specified to use auto-commit. For a non-transactional database, null
must be specified.
Note that transactionally protected operations on a Database handle
require that the Database handle itself be transactionally protected
during its open, either with a non-null transaction handle, or by calling
DatabaseConfig.setTransactional on the configuration object.
fileName - The name of an underlying file that will be used to back the database.
On Windows platforms, this argument will be interpreted as a UTF-8
string, which is equivalent to ASCII for Latin characters.
databaseName - An optional parameter that allows applications to have multiple
databases in a single file. Although no databaseName parameter needs
to be specified, it is an error to attempt to open a second database in
a physical file that was not initially created using a databaseName
parameter. Further, the databaseName parameter is not supported by the
Queue format.
config - The database open attributes. If null, default attributes are used.
DatabaseException
FileNotFoundException
public SecondaryDatabase openSecondaryDatabase(Transaction txn,
String fileName,
String databaseName,
Database primaryDatabase,
SecondaryConfig config)
throws DatabaseException,
FileNotFoundException
The database is represented by the file and database parameters.
The currently supported database file formats (or access methods) are Btree, Hash, Queue, and Recno. The Btree format is a representation of a sorted, balanced tree structure. The Hash format is an extensible, dynamic hashing scheme. The Queue format supports fast access to fixed-length records accessed sequentially or by logical record number. The Recno format supports fixed- or variable-length records, accessed sequentially or by logical record number, and optionally backed by a flat text file.
Storage and retrieval are based on key/data pairs; see DatabaseEntry
for more information.
Opening a database is a relatively expensive operation, and maintaining a set of open databases will normally be preferable to repeatedly opening and closing the database for each new query.
In-memory databases never intended to be preserved on disk may be
created by setting both the fileName and databaseName parameters to
null. Note that in-memory databases can only ever be shared by sharing
the single database handle that created them, in circumstances where
doing so is safe. The environment variable TMPDIR may
be used as a directory in which to create temporary backing files.
txn - For a transactional database, an explicit transaction may be specified, or null
may be specified to use auto-commit. For a non-transactional database, null
must be specified.
Note that transactionally protected operations on a Database handle
require that the Database handle itself be transactionally protected
during its open, either with a non-null transaction handle, or by calling
DatabaseConfig.setTransactional on the configuration object.
fileName - The name of an underlying file that will be used to back the database.
On Windows platforms, this argument will be interpreted as a UTF-8
string, which is equivalent to ASCII for Latin characters.
databaseName - An optional parameter that allows applications to have multiple
databases in a single file. Although no databaseName parameter needs
to be specified, it is an error to attempt to open a second database in
a physical file that was not initially created using a databaseName
parameter. Further, the databaseName parameter is not supported by the
Queue format.
primaryDatabase - a database handle for the primary database that is to be indexed.
config - The secondary database open attributes. If null, default attributes are used.
DatabaseException
FileNotFoundException
public void removeDatabase(Transaction txn,
String fileName,
String databaseName)
throws DatabaseException,
FileNotFoundException
Remove a database.
If no database is specified, the underlying file specified is removed.
Applications should never remove databases with open Database
handles, or in the case of removing a file, when any database in the
file has an open handle. For example, some architectures do not permit
the removal of files with open system handles. On these architectures,
attempts to remove databases currently in use by any thread of control
in the system may fail.
The environment variable DB_HOME may be used as the path of the database environment home.
This method is affected by any database directory specified with
EnvironmentConfig.addDataDir, or by setting the "set_data_dir"
string in the database environment's DB_CONFIG file.
The Database handle may not be accessed
again after this method is called, regardless of this method's success
or failure.
txn - For a transactional database, an explicit transaction may be specified, or null
may be specified to use auto-commit. For a non-transactional database, null
must be specified.
fileName - The physical file which contains the database to be removed.
On Windows platforms, this argument will be interpreted as a UTF-8
string, which is equivalent to ASCII for Latin characters.
databaseName - The database to be removed.
DeadlockException - if the operation was selected to resolve a
deadlock.
DatabaseException - if a failure occurs.
FileNotFoundException
public void renameDatabase(Transaction txn,
String fileName,
String oldDatabaseName,
String newDatabaseName)
throws DatabaseException,
FileNotFoundException
Rename a database.
If no database name is specified, the underlying file specified is renamed, incidentally renaming all of the databases it contains.
Applications should never rename databases that are currently in use. If an underlying file is being renamed and logging is currently enabled in the database environment, no database in the file may be open when this method is called. In particular, some architectures do not permit renaming files with open handles. On these architectures, attempts to rename databases that are currently in use by any thread of control in the system may fail.
The environment variable DB_HOME may be used as the path of the database environment home.
This method is affected by any database directory specified with
EnvironmentConfig.addDataDir, or by setting the "set_data_dir"
string in the database environment's DB_CONFIG file.
The Database handle may not be accessed
again after this method is called, regardless of this method's success
or failure.
txn - For a transactional database, an explicit transaction may be specified, or null
may be specified to use auto-commit. For a non-transactional database, null
must be specified.
fileName - The physical file which contains the database to be renamed.
On Windows platforms, this argument will be interpreted as a UTF-8
string, which is equivalent to ASCII for Latin characters.
oldDatabaseName - The database to be renamed.
newDatabaseName - The new name of the database or file.
DeadlockException - if the operation was selected to resolve a
deadlock.
DatabaseException - if a failure occurs.
FileNotFoundException
public int trickleCacheWrite(int percent)
throws DatabaseException
The purpose of this method is to enable a memory pool manager to ensure that a page is always available for reading in new information without having to wait for a write.
percent - The percent of the pages in the cache that should be clean.
DatabaseException - if a failure occurs.
public int detectDeadlocks(LockDetectMode mode)
throws DatabaseException
The deadlock detector traverses the lock table and marks one of the participating lock requesters for rejection in each deadlock it finds.
mode - Which lock request(s) to reject.
DatabaseException - if a failure occurs.
public Lock getLock(int locker,
boolean noWait,
DatabaseEntry object,
LockRequestMode mode)
throws DatabaseException
locker - An unsigned 32-bit integer quantity representing the entity
requesting the lock.
mode - The lock mode.
noWait - If a lock cannot be granted because the requested lock conflicts
with an existing lock, throw a LockNotGrantedException
immediately instead of waiting for the lock to become available.
object - An untyped byte string that specifies the object to be locked.
Applications using the locking subsystem directly while also doing
locking via the Berkeley DB access methods must take care not to
inadvertently lock objects that happen to be equal to the unique
file IDs used to lock files.
DatabaseException - if a failure occurs.
public void putLock(Lock lock)
throws DatabaseException
lock - The lock to be released.
DatabaseException - if a failure occurs.
public int createLockerID()
throws DatabaseException
The locker ID is guaranteed to be unique for the database environment.
Call Environment.freeLockerID to return the locker ID to
the environment when it is no longer needed.
DatabaseException
public void freeLockerID(int id)
throws DatabaseException
id - The locker id to be freed.
DatabaseException - if a failure occurs.
public void lockVector(int locker,
boolean noWait,
LockRequest[] list)
throws DatabaseException
If any of the requested locks cannot be acquired, or any of the locks to be released cannot be released, the operations before the failing operation are guaranteed to have completed successfully, and the method throws an exception.
noWait - If a lock cannot be granted because the requested lock conflicts
with an existing lock, throw a LockNotGrantedException
immediately instead of waiting for the lock to become available.
The index of the request that was not granted will be returned by
LockNotGrantedException.getIndex.
locker - An unsigned 32-bit integer quantity representing the entity
requesting the lock.
list - An array of LockRequest objects, listing the requested lock
operations.
DatabaseException - if a failure occurs.
public LogCursor openLogCursor()
throws DatabaseException
DatabaseException - if a failure occurs.
public String getLogFileName(LogSequenceNumber lsn)
throws DatabaseException
This mapping of LogSequenceNumber objects to files is needed for database administration. For example, a transaction manager typically records the earliest LogSequenceNumber object needed for restart, and the database administrator may want to archive log files to tape when they contain only log records before the earliest one needed for restart.
lsn - The LogSequenceNumber object for which a filename is wanted.
IllegalArgumentException - if an invalid parameter was specified.
DatabaseException - if a failure occurs.
public void setReplicationConfig(ReplicationConfig config,
boolean onoff)
throws DatabaseException
The database environment's replication subsystem may also be set using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "rep_set_config", one or more whitespace characters, and the method configuration parameter as a string; for example, "rep_set_config REP_CONF_NOWAIT". Because the DB_CONFIG file is read when the database environment is opened, it will silently overrule configuration done before that time.
This method configures a database environment, including all threads
of control accessing the database environment, not only the operations
performed using a specified Environment handle.
This method may be called at any time during the life of the application.
config - A replication feature to be configured.onoff - If true, the feature is enabled, otherwise it is disabled.
DatabaseException
public boolean getReplicationConfig(ReplicationConfig config)
throws DatabaseException
DatabaseException
public int electReplicationMaster(int nsites,
int nvotes,
int priority,
int timeout)
throws DatabaseException
If the election is successful, the new master's ID may be the ID of the previous master, or the ID of the current environment. The application is responsible for adjusting its usage of the other environments in the replication group, including directing all database updates to the newly selected master, in accordance with the results of this election.
The thread of control that calls this method must not be the thread of control that processes incoming messages; processing the incoming messages is necessary to successfully complete an election.
nsites - The number of environments that the application believes are in the
replication group. This number is used by Berkeley DB to avoid
having two masters active simultaneously, even in the case of a
network partition. During an election, a new master cannot be
elected unless more than half of nsites agree on the new master.
Thus, in the face of a network partition, the side of the partition
with more than half the environments will elect a new master and
continue, while the environments communicating with fewer than half
the other environments will fail to find a new master.
nvotes - The number of votes required by the application to successfully
elect a new master. It must be a positive integer, no greater than
nsites, or 0 if the election should use a simple majority of the
nsites value as the requirement. A warning is given if half or
fewer votes are required to win an election as that can potentially
lead to multiple masters in the face of a network partition.
priority - The priority of this environment. It must be a positive integer,
or 0 if this environment is not permitted to become a master.
timeout - A timeout period for an election. If the election has not completed
after timeout microseconds, the election will fail.
DatabaseException - if a failure occurs.
public ReplicationStatus processReplicationMessage(DatabaseEntry control,
DatabaseEntry rec,
int envid)
throws DatabaseException
For implementation reasons, all incoming replication messages must
be processed using the same Environment handle. It is not
required that a single thread of control process all messages, only
that all threads of control processing messages use the same handle.
control - A copy of the control parameter specified by Berkeley DB on the
sending environment.
envid - The local identifier that corresponds to the environment that sent
the message to be processed.
rec - A copy of the rec parameter specified by Berkeley DB on the sending
environment.
ReplicationStatus object.
DatabaseException
public void startReplication(DatabaseEntry cdata,
boolean master)
throws DatabaseException
The enclosing database environment must already have been configured
to send replication messages by calling EnvironmentConfig.setReplicationTransport.
cdata - An opaque data item that is sent over the communication infrastructure
when the client or master comes online. If no such information is
useful, cdata should be null.
master - Configure the environment as a replication master. If false, the
environment will be configured as as a replication client.
DatabaseException - if a failure occurs.
public void syncReplication()
throws DatabaseException
ReplicationConfig.DELAYCLIENT with
setReplicationConfig(com.sleepycat.db.ReplicationConfig, boolean).
When a client application receives a return value from processReplicationMessage(com.sleepycat.db.DatabaseEntry, com.sleepycat.db.DatabaseEntry, int) where ReplicationStatus.isNewMaster()
returns true and the application has configured delayed
synchronization, the application must choose when to perform
synchronization by using this method. Otherwise the client will remain
unsynchronized and will ignore all new incoming log messages.
This method may not be called before the database environment is opened.
DatabaseException - if a failure occurs.
public CacheStats getCacheStats(StatsConfig config)
throws DatabaseException
DatabaseException
public CacheFileStats[] getCacheFileStats(StatsConfig config)
throws DatabaseException
config - The statistics attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public LogStats getLogStats(StatsConfig config)
throws DatabaseException
config - The statistics attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public MutexStats getMutexStats(StatsConfig config)
throws DatabaseException
config - The statistics attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public ReplicationStats getReplicationStats(StatsConfig config)
throws DatabaseException
config - The statistics attributes. If null, default attributes are used.
DatabaseException - if a failure occurs.
public void logFlush(LogSequenceNumber lsn)
throws DatabaseException
lsn - All log records with LogSequenceNumber values less than or equal to
the lsn parameter are written to stable storage. If lsn is null,
all records in the log are flushed.
DatabaseException - if a failure occurs.
public LogSequenceNumber logPut(DatabaseEntry data,
boolean flush)
throws DatabaseException
data - The record to append to the log.
The caller is responsible for providing any necessary structure to data. (For example, in a write-ahead logging protocol, the application must understand what part of data is an operation code, what part is redo information, and what part is undo information. In addition, most transaction managers will store in data the LogSequenceNumber of the previous log record for the same transaction, to support chaining back through the transaction's log records during undo.)
flush - The log is forced to disk after this record is written, guaranteeing
that all records with LogSequenceNumber values less than or equal
to the one being "put" are on disk before this method returns.
DatabaseException - if a failure occurs.
public void logPrint(Transaction txn,
String message)
throws DatabaseException
This method allows applications to include information in the database environment log files, for later review using the db_printlog utility. This method is intended for debugging and performance tuning.
txn - If the logged message refers to an application-specified transaction,
the txn parameter is a transaction handle, otherwise
null.
DatabaseException - if a failure occurs.
public File[] getArchiveLogFiles(boolean includeInUse)
throws DatabaseException
This method returns the names of all of the log files that are no longer in use (for example, that are no longer involved in active transactions), and that may safely be archived for catastrophic recovery and then removed from the system. If there are no filenames to return, the method returns null.
Log cursor handles (returned by the Environment.openLogCursor) may have open file descriptors for log files in the
database environment. Also, the Berkeley DB interfaces to the
database environment logging subsystem (for example,
logPut Environment logPut and Transaction.abort may
allocate log cursors and have open file descriptors for log files
as well. On operating systems where filesystem related system calls
(for example, rename and unlink on Windows/NT) can fail if a process
has an open file descriptor for the affected file, attempting to
move or remove the log files listed by this method may fail. All
Berkeley DB internal use of log cursors operates on active log files
only and furthermore, is short-lived in nature. So, an application
seeing such a failure should be restructured to close any open log
cursors it may have, and otherwise to retry the operation until it
succeeds. (Although the latter is not likely to be necessary; it
is hard to imagine a reason to move or rename a log file in which
transactions are being logged or aborted.)
includeInUse - Return all the log filenames, regardless of whether or not they are
in use.
DatabaseException - if a failure occurs.
public File[] getArchiveDatabases()
throws DatabaseException
If any of the database files have not been accessed during the lifetime of the current log files, their names will not be included in this list. It is also possible that some of the files referred to by the log have since been deleted from the system.
DatabaseException - if a failure occurs.
public void removeOldLogFiles()
throws DatabaseException
Automatic log file removal is likely to make catastrophic recovery impossible.
DatabaseException - if a failure occurs.
public PreparedTransaction[] recover(int count,
boolean continued)
throws DatabaseException
This method should only be called after the environment has been
recovered. Because database environment state must be preserved
between recovery and the application calling this method,
applications must either call this method using the same environment
handle used when recovery is done, or the database environment must
not be configured using the EnvironmentConfig.setPrivate
method.
This method returns a list of transactions that must be resolved by the application (either committed, aborted or discarded). The return value is an array of objects of type DbPreplist.
The application must call Transaction.abort,
Transaction.commit or Transaction.discard on
each returned Transaction handle before starting any new
operations.
count - The maximum number of transactions to return.
continued - If false, begin returning a list of prepared, but not yet resolved
transactions. If true, continue returning a list of prepared
transactions, starting where the last call to this method left off.
DatabaseException
public void panic(boolean onoff)
throws DatabaseException
RunRecoveryException.
This method configures a database environment, including all threads
of control accessing the database environment, not only the operations
performed using a specified Environment handle.
This method may be called at any time during the life of the application.
onoff - If true, set the panic state for the database environment.
DatabaseExceptionpublic static String getVersionString()
This method may be called at any time during the life of the application.
public static int getVersionMajor()
This method may be called at any time during the life of the application.
public static int getVersionMinor()
This method may be called at any time during the life of the application.
public static int getVersionPatch()
This method may be called at any time during the life of the application.
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