Berkeley DB Reference Guide: Release 3.0: database open/close
Description: 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++

### Berkeley DB Reference Guide: Upgrading Berkeley DB Applications |

### Release 3.0: database open/close

Database opens were changed in the Berkeley DB 3.0 release in a similar way to environment opens.

To upgrade your application, first find each place your application opens a database, that is, calls the db_open function. Each of these calls should be replaced with calls to db_create and DB->open.

Here's an example creating a Berkeley DB database using the 2.X interface:

>     DB *dbp;
>     DB_ENV *dbenv;
>     int ret;

>     if ((ret = db_open(DATABASE,
>         DB_BTREE, DB_CREATE, 0664, dbenv, NULL, &dbp)) != 0)
>     	return (ret);

In the Berkeley DB 3.0 release, this code would be written as:

>     DB *dbp;
>     DB_ENV *dbenv;
>     int ret;

>     if ((ret = db_create(&dbp, dbenv, 0)) != 0)
>     	return (ret);

>     if ((ret = dbp->open(dbp,
>         DATABASE, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
>     	(void)dbp->close(dbp, 0);
>     	return (ret);
>     }

As you can see, the arguments to db_open and to DB->open are largely the same. There is some re-organization, and note that the enclosing DB_ENV structure is specified when the DB object is created using the db_create function. There is one additional argument to DB->open, argument #3. For backward compatibility with the 2.X Berkeley DB releases, simply set that argument to NULL.

There are two additional issues with the db_open call.

First, it was possible in the 2.X releases for an application to provide an environment that did not contain a shared memory buffer pool as the database environment, and Berkeley DB would create a private one automatically. This functionality is no longer available, applications must specify the DB_INIT_MPOOL flag if databases are going to be opened in the environment.

The final issue with upgrading the db_open call is that the DB_INFO structure is no longer used, having been replaced by individual methods on the DB handle. That change is discussed in detail later in this chapter.

Copyright (c) 1996,2007 Oracle. All rights reserved.