Berkeley DB: DbTxnMgr.unlink
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,b+tree,btr ee,hash,hashing,transaction,transactions,locking,logging,access method,access me thods,java,C,C++

# DbTxnMgr.unlink

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    import com.sleepycat.db.*;

    public static void unlink(String dir, int force, DbEnv dbenv)
    	throws DbException;

# Description

The DbTxnMgr.unlink function destroys the transaction region identified by the directory dir, removing all files used to implement the transaction region. (The directory dir is not removed.)

If there are processes that have called DbTxnMgr.open without calling DbTxnMgr.close (i.e., there are processes currently using the transaction region), DbTxnMgr.unlink will fail without further action, unless the force flag is set, in which case DbTxnMgr.unlink will attempt to remove the transaction region files regardless of any processes still using it.

The result of attempting to forcibly destroy the region when a process has the region open is unspecified. Processes using a shared memory region maintain an open file descriptor for it. On UNIX systems, the region removal should succeed and processes that have already joined the region should continue to run in the region without change, however processes attempting to join the transaction region will either fail or attempt to create a new region. On other systems (e.g., Windows/NT), where the unlink(2) system call will fail if any process has an open file descriptor for the file, the region removal will fail.

In the case of catastrophic or system failure, database recovery must be performed (see db_recover), or the DB_RECOVER and DB_RECOVER_FATAL flags to DbEnv.appinit must be specified. Alternatively, if recovery is not required because no database state is maintained across failures, it is possible to clean up a transaction region by removing all of the files in the directory specified to the DbTxnMgr.open function, as no transaction region files are created in any other directory. Note, however, that this has the potential to remove files created by the other Berkeley DB subsystems in the same database environment.

The DbTxnMgr.unlink method throws an exception that encapsulates an errno on failure.

# Errors

If a fatal error occurs in Berkeley DB, the DbTxnMgr.unlink method may fail and throw a DbRunRecoveryException, at which point all subsequent database calls will also fail in the same way.

The DbTxnMgr.unlink method may fail and throw an exception for any of the errors specified for the following Berkeley DB and C library functions: abort(3), close(3), DbEnv.version, fcntl(3), fflush(3), fprintf(3), free(3), fstat(3), fsync(3), getenv(3), getpid(3), getuid(3), isdigit(3), lseek(3), malloc(3), memcpy(3), memset(3), mmap(3), munmap(3), open(3), pstat_getdynamic(3), read(3), shmat(3), shmctl(3), shmdt(3), sigfillset(3), sigprocmask(3), stat(3), strerror(3), strlen(3), sysconf(3), unlink(3), vfprintf(3), vsnprintf(3), and write(3).

In addition, the DbTxnMgr.unlink method may fail and throw an exception encapsulating errno for the following conditions:

EBUSY
  The shared memory region was in use and the force flag was not set.

# Class

DbTxnMgr

# See Also

DbTxnMgr.begin, DbTxnMgr.checkpoint, DbTxnMgr.close, DbTxnMgr.open, DbTxnMgr.stat and DbTxnMgr.unlink.`