diff options
Diffstat (limited to 'bdb/docs/ref/am_conf/re_source.html')
| -rw-r--r-- | bdb/docs/ref/am_conf/re_source.html | 62 |
1 files changed, 0 insertions, 62 deletions
diff --git a/bdb/docs/ref/am_conf/re_source.html b/bdb/docs/ref/am_conf/re_source.html deleted file mode 100644 index 2095a96983a..00000000000 --- a/bdb/docs/ref/am_conf/re_source.html +++ /dev/null @@ -1,62 +0,0 @@ -<!--$Id: re_source.so,v 10.14 2000/11/20 21:45:19 bostic Exp $--> -<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.--> -<!--All rights reserved.--> -<html> -<head> -<title>Berkeley DB Reference Guide: Flat-text backing files</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> - <a name="2"><!--meow--></a> -<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_conf/extentsize.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_conf/renumber.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p> -<h1 align=center>Flat-text backing files</h1> -<p>It is possible to back any Recno database (either fixed or variable -length) with a flat-text source file. This provides fast read (and -potentially write) access to databases that are normally created and -stored as flat-text files. The backing source file may be specified by -calling the <a href="../../api_c/db_set_re_source.html">DB->set_re_source</a> function. -<p>The backing source file will be read to initialize the database. In the -case of variable length records, the records are assumed to be separated -as described for the <a href="../../api_c/db_set_re_delim.html">DB->set_re_delim</a> function interface. For example, -standard UNIX byte stream files can be interpreted as a sequence of -variable length records separated by ASCII newline characters. This is -the default. -<p>When cached data would normally be written back to the underlying database -file (e.g., <a href="../../api_c/db_close.html">DB->close</a> or <a href="../../api_c/db_sync.html">DB->sync</a> functions are called), the -in-memory copy of the database will be written back to the backing source -file. -<p>The backing source file must already exist (but may be zero-length) when -<a href="../../api_c/db_open.html">DB->open</a> is called. By default, the backing source file is read -lazily, i.e., records are not read from the backing source file until they -are requested by the application. If multiple processes (not threads) are -accessing a Recno database concurrently and either inserting or deleting -records, the backing source file must be read in its entirety before more -than a single process accesses the database, and only that process should -specify the backing source file as part of the <a href="../../api_c/db_open.html">DB->open</a> call. -This can be accomplished by calling the <a href="../../api_c/db_set_flags.html">DB->set_flags</a> function with the -<a href="../../api_c/db_set_flags.html#DB_SNAPSHOT">DB_SNAPSHOT</a> flag. -<p>Reading and writing the backing source file cannot be transactionally -protected because it involves filesystem operations that are not part of -the Berkeley DB transaction methodology. For this reason, if a temporary -database is used to hold the records (a NULL was specified as the file -argument to <a href="../../api_c/db_open.html">DB->open</a>), <b>it is possible to lose the -contents of the backing source file if the system crashes at the right -instant</b>. If a permanent file is used to hold the database (a file name -was specified as the file argument to <a href="../../api_c/db_open.html">DB->open</a>), normal database -recovery on that file can be used to prevent information loss. It is -still possible that the contents of the backing source file itself will -be corrupted or lost if the system crashes. -<p>For all of the above reasons, the backing source file is generally used -to specify databases that are read-only for Berkeley DB applications, and that -are either generated on the fly by software tools, or modified using a -different mechanism such as a text editor. -<table><tr><td><br></td><td width="1%"><a href="../../ref/am_conf/extentsize.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_conf/renumber.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> |