- Berkeley DB Reference Guide:
- Environment
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A Berkeley DB environment is an encapsulation of one or more databases, log files and region files. Region files are the shared memory areas that contain information about the database environment such as memory pool cache pages. Only databases are byte-order independent and only database files can be moved between machines of different byte orders. Log files can be moved between machines of the same byte order. Region files are usually unique to a specific machine and potentially to a specific operating system release.
The simplest way to administer a Berkeley DB application environment is to create a single home directory that stores the files for the applications that will share the environment. The environment home directory must be created before any Berkeley DB applications are run. Berkeley DB itself never creates the environment home directory. The environment can then be identified by the name of that directory.
An environment may be shared by any number of processes, as well as by any number of threads within those processes. It is possible for an environment to include resources from other directories on the system, and applications often choose to distribute resources to other directories or disks for performance or other reasons. However, by default, the databases, shared regions (the locking, logging, memory pool, and transaction shared memory areas) and log files will be stored in a single directory hierarchy.
It is important to realize that all applications sharing a database environment implicitly trust each other. They have access to each other's data as it resides in the shared regions, and they will share resources such as buffer space and locks. At the same time, any applications using the same databases must share an environment if consistency is to be maintained between them.
| Database Environments and Related Methods | Description |
|---|---|
| db_env_create | Create an environment handle |
| DB_ENV->close | Close an environment |
| DB_ENV->dbremove | Remove a database |
| DB_ENV->dbrename | Rename a database |
| DB_ENV->err | Error message with error string |
| DB_ENV->errx | Error message |
| DB_ENV->lock_detect | Perform deadlock detection |
| DB_ENV->lock_get | Acquire a lock |
| DB_ENV->lock_id | Acquire a locker ID |
| DB_ENV->lock_id_free | Release a locker ID |
| DB_ENV->lock_put | Release a lock |
| DB_ENV->lock_stat | Return lock subsystem statistics |
| DB_ENV->lock_vec | Acquire/release locks |
| DB_ENV->log_archive | List log and database files |
| DB_ENV->log_cursor | Create a log cursor handle |
| DB_ENV->log_file | Map Log Sequence Numbers to log files |
| DB_ENV->log_flush | Flush log records |
| DB_ENV->log_put | Write a log record |
| DB_ENV->log_stat | Return log subsystem statistics |
| DB_ENV->memp_fcreate | Open a file in a memory pool |
| DB_ENV->memp_register | Register input/output functions for a file in a memory pool |
| DB_ENV->memp_stat | Return memory pool statistics |
| DB_ENV->memp_sync | Flush pages from a memory pool |
| DB_ENV->memp_trickle | Trickle flush pages from a memory pool |
| DB_ENV->open | Open an environment |
| DB_ENV->remove | Remove an environment |
| DB_ENV->rep_elect | Hold a replication election |
| DB_ENV->rep_process_message | Process a replication message |
| DB_ENV->rep_start | Configure an environment for replication |
| DB_ENV->rep_stat | Replication statistics |
| DB_ENV->set_alloc | Set local space allocation functions |
| DB_ENV->set_app_dispatch | Configure application recovery |
| DB_ENV->set_cachesize | Set the environment cache size |
| DB_ENV->set_data_dir | Set the environment data directory |
| DB_ENV->set_encrypt | Set the environment cryptographic key |
| DB_ENV->set_errcall | Set error message callback |
| DB_ENV->set_errfile | Set error message FILE |
| DB_ENV->set_errpfx | Set error message prefix |
| DB_ENV->set_feedback | Set feedback callback |
| DB_ENV->set_flags | Environment configuration |
| DB_ENV->set_lg_bsize | Set log buffer size |
| DB_ENV->set_lg_dir | Set the environment logging directory |
| DB_ENV->set_lg_max | Set log file size |
| DB_ENV->set_lg_regionmax | Set logging region size |
| DB_ENV->set_lk_conflicts | Set lock conflicts matrix |
| DB_ENV->set_lk_detect | Set automatic deadlock detection |
| DB_ENV->set_lk_max_lockers | Set maximum number of lockers |
| DB_ENV->set_lk_max_locks | Set maximum number of locks |
| DB_ENV->set_lk_max_objects | Set maximum number of lock objects |
| DB_ENV->set_mp_mmapsize | Set maximum mapped-in database file size |
| DB_ENV->set_paniccall | Set panic callback |
| DB_ENV->set_rep_limit | Limit data sent in response to a single message |
| DB_ENV->set_rep_transport | Configure replication transport |
| DB_ENV->set_rpc_server | Establish an RPC server connection |
| DB_ENV->set_shm_key | Set system memory shared segment ID |
| DB_ENV->set_tas_spins | Set the number of test-and-set spins |
| DB_ENV->set_timeout | Set lock and transaction timeout |
| DB_ENV->set_tmp_dir | Set the environment temporary file directory |
| DB_ENV->set_tx_max | Set maximum number of transactions |
| DB_ENV->set_tx_timestamp | Set recovery timestamp |
| DB_ENV->set_verbose | Set verbose messages |
| DB_ENV->txn_begin | Begin a transaction |
| DB_ENV->txn_checkpoint | Checkpoint the transaction subsystem |
| DB_ENV->txn_recover | Distributed transaction recovery |
| DB_ENV->txn_stat | Return transaction subsystem statistics |
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