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diff --git a/bdb/docs/ref/am/opensub.html b/bdb/docs/ref/am/opensub.html deleted file mode 100644 index 066ca4b7933..00000000000 --- a/bdb/docs/ref/am/opensub.html +++ /dev/null @@ -1,64 +0,0 @@ -<!--$Id: opensub.so,v 10.6 2000/12/18 21:05:14 bostic Exp $--> -<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.--> -<!--All rights reserved.--> -<html> -<head> -<title>Berkeley DB Reference Guide: Opening multiple databases in a single file</title> -<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> -<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++"> -</head> -<body bgcolor=white> -<table><tr valign=top> -<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Access Methods</dl></h3></td> -<td width="1%"><a href="../../ref/am/open.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/am/upgrade.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p> -<h1 align=center>Opening multiple databases in a single file</h1> -<p>Applications may create multiple databases within a single physical -file. This is useful when the databases are both numerous and -reasonably small, in order to avoid creating a large number of -underlying files, or when it is desirable to include secondary index -databases in the same file as the primary index database. Multiple -databases are an administrative convenience and using them is unlikely -to effect database performance. To open or create a file that will -include more than a single database, specify a database name when -calling the <a href="../../api_c/db_open.html">DB->open</a> method. -<p>Physical files do not need to be comprised of a single type of database, -and databases in a file may be of any type (e.g., Btree, Hash or Recno), -except for Queue databases. Queue databases must be created one per file -and cannot share a file with any other database type. There is no limit -on the number of databases that may be created in a single file other than -the standard Berkeley DB file size and disk space limitations. -<p>It is an error to attempt to open a second database in a file that was -not initially created using a database name, that is, the file must -initially be specified as capable of containing multiple databases for a -second database to be created in it. -<p>It is not an error to open a file that contains multiple databases without -specifying a database name, however the database type should be specified -as DB_UNKNOWN and the database must be opened read-only. The handle that -is returned from such a call is a handle on a database whose key values -are the names of the databases stored in the database file and whose data -values are opaque objects. No keys or data values may be modified or -stored using this database handle. -<p>Storing multiple databases in a single file is almost identical to -storing each database in its own separate file. The one crucial -difference is how locking and the underlying memory pool services must -to be configured. As an example, consider two databases instantiated -in two different physical files. If access to each separate database -is single-threaded, there is no reason to perform any locking of any -kind, and the two databases may be read and written simultaneously. -Further, there would be no requirement to create a shared database -environment in which to open the databases. Because multiple databases -in a file exist in a single physical file, opening two databases in the -same file requires that locking be enabled, unless access to the -databases is known to be single-threaded, that is, only one of the -databases is ever accessed at a time. (As the locks for the two -databases can only conflict during page allocation, this additional -locking is unlikely to effect performance.) Further, the databases must -share an underlying memory pool so that per-physical-file information -is updated correctly. -<table><tr><td><br></td><td width="1%"><a href="../../ref/am/open.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/am/upgrade.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font> -</body> -</html> |