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diff --git a/bdb/docs/ref/arch/bigpic.html b/bdb/docs/ref/arch/bigpic.html deleted file mode 100644 index 6c945744e83..00000000000 --- a/bdb/docs/ref/arch/bigpic.html +++ /dev/null @@ -1,114 +0,0 @@ -<!--$Id: bigpic.so,v 8.21 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: The big picture</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>Architecture</dl></h3></td> -<td width="1%"><a href="../../ref/am/error.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/arch/progmodel.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p> -<h1 align=center>The big picture</h1> -<p>The previous chapters in this Reference Guide have described applications -that use the Berkeley DB Access Methods for fast data storage and retrieval. -The applications we describe here and in subsequent chapters are similar -in nature to the Access Method applications, but they are also fully -recoverable in the face of application or system failure. -<p>Application code that only uses the Berkeley DB Access Methods might appear as -follows: -<p><blockquote><pre>switch (ret = dbp->put(dbp, NULL, &key, &data, 0)) { -case 0: - printf("db: %s: key stored.\n", (char *)key.data); - break; -default: - dbp->err(dbp, ret, "dbp->put"); - exit (1); -}</pre></blockquote> -<p>The underlying Berkeley DB architecture that supports this is: -<p align=center><img src="smallpic.gif" alt="small"> -<p>As you can see from this diagram, the application makes calls into the -Access Methods, and the Access Methods use the underlying shared memory -buffer cache to hold recently used file pages in main memory. -<p>When applications require recoverability, then their calls to the Access -Methods must be wrapped in calls to the transaction subsystem. The -application must inform Berkeley DB where to begin and end transactions, and -must be prepared for the possibility that an operation may fail at any -particular time, causing the transaction to abort. -<p>An example of transaction protected code might appear as follows: -<p><blockquote><pre>retry: if ((ret = txn_begin(dbenv, NULL, &tid)) != 0) { - dbenv->err(dbenv, ret, "txn_begin"); - exit (1); - } -<p> - switch (ret = dbp->put(dbp, tid, &key, &data, 0)) { - case DB_LOCK_DEADLOCK: - (void)txn_abort(tid); - goto retry; - case 0: - printf("db: %s: key stored.\n", (char *)key.data); - break; - default: - dbenv->err(dbenv, ret, "dbp->put"); - exit (1); - } -<p> - if ((ret = txn_commit(tid)) != 0) { - dbenv->err(dbenv, ret, "txn_commit"); - exit (1); - }</pre></blockquote> -<p>In this example, the same operation is being done as before, however, it -is wrapped in transaction calls. The transaction is started with -<a href="../../api_c/txn_begin.html">txn_begin</a>, and finished with <a href="../../api_c/txn_commit.html">txn_commit</a>. If the operation -fails due to a deadlock, then the transaction is aborted using -<a href="../../api_c/txn_abort.html">txn_abort</a>, after which the operation may be retried. -<p>There are actually five major subsystems in Berkeley DB, as follows: -<p><dl compact> -<p><dt>The Access Methods<dd>The Access Method subsystem provides general-purpose support for creating -and accessing database files formatted as Btrees, Hashed files, and -Fixed- and Variable-length records. These modules are useful in the -absence of transactions for applications that need fast, formatted file -support. See <a href="../../api_c/db_open.html">DB->open</a> and <a href="../../api_c/db_cursor.html">DB->cursor</a> for more -information. These functions were already discussed in detail in the -previous chapters. -<p><dt>The Memory Pool<dd>The memory pool subsystem is the general-purpose shared memory buffer pool -used by Berkeley DB. This is the shared memory cache that allows multiple -processes and threads within processes to share access to databases. This -module is useful outside of the Berkeley DB package for processes that require -portable, page-oriented, cached, shared file access. -<p><dt>Transactions<dd>The transaction subsystem allows a group of database changes to be -treated as an atomic unit so that either all of the changes are done, or -none of the changes are done. The transaction subsystem implements the -Berkeley DB transaction model. This module is useful outside of the Berkeley DB -package for processes that want to transaction protect their own data -modifications. -<p><dt>Locking<dd>The locking subsystem is the general-purpose lock manager used by Berkeley DB. -This module is useful outside of the Berkeley DB package for processes that -require a portable, fast, configurable lock manager. -<p><dt>Logging<dd>The logging subsystem is the write-ahead logging used to support the Berkeley DB -transaction model. It is largely specific to the Berkeley DB package, and -unlikely to be useful elsewhere except as a supporting module for the -Berkeley DB transaction subsystem. -</dl> -<p>Here is a more complete picture of the Berkeley DB library: -<p align=center><img src="bigpic.gif" alt="large"> -<p>In this example, the application makes calls to the Access Methods and to -the transaction subsystem. The Access Methods and transaction subsystem -in turn make calls into the Buffer Pool, Locking and Logging subsystems -on behalf of the application. -<p>While the underlying subsystems can each be called independently. For -example, the Buffer Pool subsystem can be used apart from the rest of -Berkeley DB by applications simply wanting a shared memory buffer pool, or -the Locking subsystem may be called directly by applications that are -doing their own locking outside of Berkeley DB. However, this usage is fairly -rare, and most applications will either use only the Access Methods, or -the Access Methods wrapped in calls to the transaction interfaces. -<table><tr><td><br></td><td width="1%"><a href="../../ref/am/error.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/arch/progmodel.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> |