# Berkeley DB Reference Guide: Access method operations
Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++

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Berkeley DB Reference Guide:
  Access Methods

### Access method operations

Once a database handle has been created using db_create, there are several standard access method operations. Each of these operations is performed using a method referred to by the returned handle. Generally, the database will be opened using DB->open. If the database is from an old release of Berkeley DB, it may need to be upgraded to the current release before it is opened using DB->upgrade.

Once a database has been opened, records may be retrieved (DB->get), stored (DB->put), and deleted (DB->del).

Additional operations supported by the database handle include statistics (DB->stat), truncation (DB->truncate), version upgrade (DB->upgrade), verification and salvage (DB->verify), flushing to a backing file (DB->sync), and association of secondary indices (DB->associate). Database handles are eventually closed using DB->close.

Database Operations | Description
--- | ---
db_create | Create a database handle
DB->associate | Associate a secondary index
DB->close | Close a database
DB->compact | Compact a database
DB->cursor | Create a cursor
DB->del | Delete items from a database
DB->err, DB->errx | Error message
DB->exists | Return if an item appears in a database
DB->fd | Return a file descriptor from a database
DB->get, DB->pget | Get items from a database
DB->get_byteswapped | Return if the underlying database is in host order
DB->get_type | Return the database type
DB->join | Perform a database join on cursors
DB->key_range | Return estimate of key location
DB->open | Open a database
DB->put | Store items into a database
DB->remove | Remove a database
DB->rename | Rename a database
DB->set_priority | Set cache page priority
DB->stat, DB->stat_print | Database statistics
DB->sync | Flush a database to stable storage
DB->truncate | Empty a database
DB->upgrade | Upgrade a database
DB->verify | Verify/salvage a database
Database Configuration |
DB->set_alloc | Set local space allocation functions
DB->set_cachesize | Set the database cache size
DB->set_dup_compare | Set a duplicate comparison function
DB->set_encrypt | Set the database cryptographic key
DB->set_errcall, DB->set_msgcall | Set error and informational message callback
DB->set_errfile, DB->set_msgfile | Set error and informational message FILE
DB->set_errpfx | Set error message prefix
DB->set_feedback | Set feedback callback
DB->set_flags | General database configuration
DB->set_lorder | Set the database byte order
DB->set_pagesize | Set the underlying database page size
Btree/Recno Configuration |
DB->set_append_recno | Set record append callback
DB->set_bt_compare | Set a Btree comparison function
DB->set_bt_minkey | Set the minimum number of keys per Btree page
DB->set_bt_prefix | Set a Btree prefix comparison function
DB->set_re_delim | Set the variable-length record delimiter
DB->set_re_len | Set the fixed-length record length
DB->set_re_pad | Set the fixed-length record pad byte
DB->set_re_source | Set the backing Recno text file
Hash Configuration |
DB->set_h_compare | Set a Hash comparison function
DB->set_h_ffactor | Set the Hash table density
DB->set_h_hash | Set a hashing function
DB->set_h_nelem | Set the Hash table size
Queue Configuration |
DB->set_q_extentsize | Set Queue database extent size

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