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void com::sleepycat::db::Db::setFlags ( int  flags  )  throws DbException [inline]

Configure a database. Calling Db.setFlags is additive; there is no way to clear flags.

The Db.setFlags method may not be called after the Db.open method is called.

Parameters:
flags must be set to 0 or by bitwise inclusively OR 'ing together one or more of the following values:

General

The following flags may be specified for any Berkeley DB access method:

  • Db.DB_CHKSUM

    Do checksum verification of pages read into the cache from the backing filestore. Berkeley DB uses the SHA1 Secure Hash Algorithm if encryption is configured and a general hash algorithm if it is not.

    Calling Db.setFlags with the Db.DB_CHKSUM flag only affects the specified Db handle (and any other Berkeley DB handles opened within the scope of that handle).

    If the database already exists when Db.open is called, the DB_CHKSUM flag will be ignored. If creating additional databases in a file, the checksum behavior specified must be consistent with the existing databases in the file or an error will be returned.

  • Db.DB_ENCRYPT

    Encrypt the database using the cryptographic password specified to the DbEnv.setEncrypted or Db.setEncrypted methods.

    Calling Db.setFlags with the Db.DB_ENCRYPT flag only affects the specified Db handle (and any other Berkeley DB handles opened within the scope of that handle).

    If the database already exists when Db.open is called, the DB_ENCRYPT flag must be the same as the existing database or an error will be returned. If creating additional databases in a file, the encryption behavior specified must be consistent with the existing databases in the file or an error will be returned.

    Encrypted databases are not portable between machines of different byte orders, that is, encrypted databases created on big-endian machines cannot be read on little-endian machines, and vice versa.

  • Db.DB_TXN_NOT_DURABLE

    If set, Berkeley DB will not write log records for this database. This means that updates of this database exhibit the ACI (atomicity, consistency, and isolation) properties, but not D (durability); that is, database integrity will be maintained, but if the application or system fails, integrity will not persist. The database file must be verified and/or restored from backup after a failure. In order to ensure integrity after application shut down, the database handles must be closed without specifying Db.DB_NOSYNC , or all database changes must be flushed from the database environment cache using the DbEnv.txnCheckpoint method. All database handles for a single physical file must set Db.DB_TXN_NOT_DURABLE , including database handles for different databases in a physical file.

    Calling Db.setFlags with the Db.DB_TXN_NOT_DURABLE flag only affects the specified Db handle (and any other Berkeley DB handles opened within the scope of that handle).

Btree

The following flags may be specified for the Btree access method:

  • Db.DB_DUP

    Permit duplicate data items in the database; that is, insertion when the key of the key/data pair being inserted already exists in the database will be successful. The ordering of duplicates in the database is determined by the order of insertion, unless the ordering is otherwise specified by use of a cursor operation.

    The Db.DB_DUPSORT flag is preferred to Db.DB_DUP for performance reasons. The Db.DB_DUP flag should only be used by applications wanting to order duplicate data items manually.

    Calling Db.setFlags with the Db.DB_DUP flag affects the database, including all threads of control accessing the database.

    If the database already exists when Db.open is called, the DB_DUP flag must be the same as the existing database or an error will be returned.

    It is an error to specify both Db.DB_DUP and Db.DB_RECNUM.

  • Db.DB_DUPSORT

    Permit duplicate data items in the database; that is, insertion when the key of the key/data pair being inserted already exists in the database will be successful. The ordering of duplicates in the database is determined by the duplicate comparison function. A default lexical comparison will be used. It is an error to specify both Db.DB_DUPSORT and Db.DB_RECNUM .

    Calling Db.setFlags with the Db.DB_DUPSORT flag affects the database, including all threads of control accessing the database.

    If the database already exists when Db.open is called, the DB_DUPSORT flag must be the same as the existing database or an error will be returned.

  • Db.DB_RECNUM

    Support retrieval from the Btree using record numbers. For more information, see the Db.DB_SET_RECNO flag to the Db.get and Dbc.get methods.

    Logical record numbers in Btree databases are mutable in the face of record insertion or deletion. See the Db.DB_RENUMBER flag in the Recno access method information for further discussion.

    Maintaining record counts within a Btree introduces a serious point of contention, namely the page locations where the record counts are stored. In addition, the entire database must be locked during both insertions and deletions, effectively single-threading the database for those operations. Specifying Db.DB_RECNUM can result in serious performance degradation for some applications and data sets.

    It is an error to specify both Db.DB_DUP and Db.DB_RECNUM.

    Calling Db.setFlags with the Db.DB_RECNUM flag affects the database, including all threads of control accessing the database.

    If the database already exists when Db.open is called, the DB_RECNUM flag must be the same as the existing database or an error will be returned.

  • Db.DB_REVSPLITOFF

    Turn off reverse splitting in the Btree. As pages are emptied in a database, the Berkeley DB Btree implementation attempts to coalesce empty pages into higher-level pages in order to keep the database as small as possible and minimize search time. This can hurt performance in applications with cyclical data demands; that is, applications where the database grows and shrinks repeatedly. For example, because Berkeley DB does page-level locking, the maximum level of concurrency in a database of two pages is far smaller than that in a database of 100 pages, so a database that has shrunk to a minimal size can cause severe deadlocking when a new cycle of data insertion begins.

    Calling Db.setFlags with the Db.DB_REVSPLITOFF flag only affects the specified Db handle (and any other Berkeley DB handles opened within the scope of that handle).

Hash

The following flags may be specified for the Hash access method:

  • Db.DB_DUP

    Permit duplicate data items in the database; that is, insertion when the key of the key/data pair being inserted already exists in the database will be successful. The ordering of duplicates in the database is determined by the order of insertion, unless the ordering is otherwise specified by use of a cursor operation.

    The Db.DB_DUPSORT flag is preferred to Db.DB_DUP for performance reasons. The Db.DB_DUP flag should only be used by applications wanting to order duplicate data items manually.

    Calling Db.setFlags with the Db.DB_DUP flag affects the database, including all threads of control accessing the database.

    If the database already exists when Db.open is called, the DB_DUP flag must be the same as the existing database or an error will be returned.

  • Db.DB_DUPSORT

    Permit duplicate data items in the database; that is, insertion when the key of the key/data pair being inserted already exists in the database will be successful. The ordering of duplicates in the database is determined by the duplicate comparison function. A default lexical comparison will be used. It is an error to specify both Db.DB_DUPSORT and Db.DB_RECNUM .

    Calling Db.setFlags with the Db.DB_DUPSORT flag affects the database, including all threads of control accessing the database.

    If the database already exists when Db.open is called, the DB_DUPSORT flag must be the same as the existing database or an error will be returned.

Queue

There are no additional flags that may be specified for the Queue access method.

Recno

The following flags may be specified for the Recno access method:

  • Db.DB_RENUMBER

    Specifying the Db.DB_RENUMBER flag causes the logical record numbers to be mutable, and change as records are added to and deleted from the database. For example, the deletion of record number 4 causes records numbered 5 and greater to be renumbered downward by one. If a cursor was positioned to record number 4 before the deletion, it will refer to the new record number 4, if any such record exists, after the deletion. If a cursor was positioned after record number 4 before the deletion, it will be shifted downward one logical record, continuing to refer to the same record as it did before.

    Using the Db.put or Dbc.put interfaces to create new records will cause the creation of multiple records if the record number is more than one greater than the largest record currently in the database. For example, creating record 28, when record 25 was previously the last record in the database, will create records 26 and 27 as well as 28. Attempts to retrieve records that were created in this manner will result in an error return of Db.DB_KEYEMPTY .

    If a created record is not at the end of the database, all records following the new record will be automatically renumbered upward by one. For example, the creation of a new record numbered 8 causes records numbered 8 and greater to be renumbered upward by one. If a cursor was positioned to record number 8 or greater before the insertion, it will be shifted upward one logical record, continuing to refer to the same record as it did before.

    For these reasons, concurrent access to a Recno database with the Db.DB_RENUMBER flag specified may be largely meaningless, although it is supported.

    Calling Db.setFlags with the Db.DB_RENUMBER flag affects the database, including all threads of control accessing the database.

    If the database already exists when Db.open is called, the DB_RENUMBER flag must be the same as the existing database or an error will be returned.

  • Db.DB_SNAPSHOT

    This flag specifies that any specified re_source file be read in its entirety when Db.open is called. If this flag is not specified, the re_source file may be read lazily.

    Calling Db.setFlags with the Db.DB_SNAPSHOT flag only affects the specified Db handle (and any other Berkeley DB handles opened within the scope of that handle).

Exceptions:
IllegalArgumentException The Db.setFlags method will fail and throw a IllegalArgumentException exception if an invalid flag value or parameter was specified.

Definition at line 5492 of file Db.java.

Referenced by com::sleepycat::examples::bdb::shipment::tuple::SampleDatabase::SampleDatabase(), com::sleepycat::examples::bdb::shipment::sentity::SampleDatabase::SampleDatabase(), com::sleepycat::examples::bdb::shipment::marshal::SampleDatabase::SampleDatabase(), com::sleepycat::examples::bdb::shipment::index::SampleDatabase::SampleDatabase(), com::sleepycat::examples::bdb::shipment::factory::SampleDatabase::SampleDatabase(), and com::sleepycat::examples::bdb::shipment::entity::SampleDatabase::SampleDatabase().

                                                       {
        db_javaJNI.Db_set_flags(swigCPtr, flags);
    }


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