mirror of
https://github.com/berkeleydb/libdb.git
synced 2024-11-16 17:16:25 +00:00
196 lines
7.2 KiB
HTML
196 lines
7.2 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
||
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||
<html xmlns="http://www.w3.org/1999/xhtml">
|
||
<head>
|
||
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
||
<title>Opening a Transactional Environment and Database</title>
|
||
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
||
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
||
<link rel="start" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
|
||
<link rel="up" href="enabletxn.html" title="Chapter 2. Enabling Transactions" />
|
||
<link rel="prev" href="enabletxn.html" title="Chapter 2. Enabling Transactions" />
|
||
<link rel="next" href="usingtxns.html" title="Chapter 3. Transaction Basics" />
|
||
</head>
|
||
<body>
|
||
<div xmlns="" class="navheader">
|
||
<div class="libver">
|
||
<p>Library Version 11.2.5.3</p>
|
||
</div>
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">Opening a Transactional Environment and
|
||
<span xmlns="http://www.w3.org/1999/xhtml">Database</span>
|
||
|
||
|
||
</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="enabletxn.html">Prev</a> </td>
|
||
<th width="60%" align="center">Chapter 2. Enabling Transactions</th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="usingtxns.html">Next</a></td>
|
||
</tr>
|
||
</table>
|
||
<hr />
|
||
</div>
|
||
<div class="sect1" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title" style="clear: both"><a id="envopen"></a>Opening a Transactional Environment and
|
||
<span>Database</span>
|
||
|
||
|
||
</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
To enable transactions for your environment, you must initialize the
|
||
transactional subsystem. Note that doing this also initializes the
|
||
logging subsystem. In addition, you must initialize the memory pool
|
||
(in-memory cache). You must also initialize the locking subsystem.
|
||
|
||
|
||
<span>
|
||
For example:
|
||
</span>
|
||
|
||
</p>
|
||
<pre class="programlisting">#include "db_cxx.h"
|
||
|
||
...
|
||
|
||
int main(void)
|
||
{
|
||
u_int32_t env_flags = DB_CREATE | // If the environment does not
|
||
// exist, create it.
|
||
DB_INIT_LOCK | // Initialize locking
|
||
DB_INIT_LOG | // Initialize logging
|
||
DB_INIT_MPOOL | // Initialize the cache
|
||
DB_INIT_TXN; // Initialize transactions
|
||
|
||
std::string envHome("/export1/testEnv");
|
||
DbEnv myEnv(0);
|
||
|
||
try {
|
||
|
||
myEnv.open(envHome.c_str(), env_flags, 0);
|
||
|
||
} catch(DbException &e) {
|
||
std::cerr << "Error opening database environment: "
|
||
<< envHome << std::endl;
|
||
std::cerr << e.what() << std::endl;
|
||
return (EXIT_FAILURE);
|
||
}
|
||
|
||
try {
|
||
myEnv.close(0);
|
||
} catch(DbException &e) {
|
||
std::cerr << "Error closing database environment: "
|
||
<< envHome << std::endl;
|
||
std::cerr << e.what() << std::endl;
|
||
return (EXIT_FAILURE);
|
||
}
|
||
|
||
return (EXIT_SUCCESS);
|
||
} </pre>
|
||
<p>
|
||
You then create and open your database(s) as you would for a non-transactional system.
|
||
<span>
|
||
The only difference is that you must pass the environment handle to
|
||
the
|
||
|
||
<span>
|
||
<code class="methodname">DbEnv::open()</code> method,
|
||
</span>
|
||
and you must open the database within a transaction.
|
||
Typically auto commit is used for this purpose. To do so, pass
|
||
<code class="literal">DB_AUTO_COMMIT</code> to the database open command.
|
||
It is recommended that you close all your databases before you close
|
||
your environment.
|
||
For example:
|
||
</span>
|
||
|
||
|
||
</p>
|
||
<pre class="programlisting">#include "db_cxx.h"
|
||
|
||
...
|
||
|
||
int main(void)
|
||
{
|
||
u_int32_t env_flags = DB_CREATE | // If the environment does not
|
||
// exist, create it.
|
||
DB_INIT_LOCK | // Initialize locking
|
||
DB_INIT_LOG | // Initialize logging
|
||
DB_INIT_MPOOL | // Initialize the cache
|
||
DB_INIT_TXN; // Initialize transactions
|
||
|
||
<strong class="userinput"><code>u_int32_t db_flags = DB_CREATE | DB_AUTO_COMMIT;
|
||
Db *dbp = NULL;
|
||
const char *file_name = "mydb.db";</code></strong>
|
||
|
||
std::string envHome("/export1/testEnv");
|
||
DbEnv myEnv(0);
|
||
|
||
try {
|
||
|
||
myEnv.open(envHome.c_str(), env_flags, 0);
|
||
<strong class="userinput"><code>dbp = new Db(&myEnv, 0);
|
||
dbp->open(NULL, // Txn pointer
|
||
file_name, // File name
|
||
NULL, // Logical db name
|
||
DB_BTREE, // Database type (using btree)
|
||
db_flags, // Open flags
|
||
0); // File mode. Using defaults </code></strong>
|
||
|
||
} catch(DbException &e) {
|
||
std::cerr << "Error opening database and environment: "
|
||
<< file_name << ", "
|
||
<< envHome << std::endl;
|
||
std::cerr << e.what() << std::endl;
|
||
}
|
||
|
||
try {
|
||
<strong class="userinput"><code>dbp->close(0);</code></strong>
|
||
myEnv.close(0);
|
||
} catch(DbException &e) {
|
||
std::cerr << "Error closing database and environment: "
|
||
<< file_name << ", "
|
||
<< envHome << std::endl;
|
||
std::cerr << e.what() << std::endl;
|
||
return (EXIT_FAILURE);
|
||
}
|
||
|
||
return (EXIT_SUCCESS);
|
||
} </pre>
|
||
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
|
||
<h3 class="title">Note</h3>
|
||
<p>
|
||
Never close a database that has active transactions. Make sure
|
||
all transactions are resolved (either committed or aborted)
|
||
before closing the database.
|
||
</p>
|
||
</div>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="enabletxn.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="enabletxn.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="usingtxns.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">Chapter 2. Enabling Transactions </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Chapter 3. Transaction Basics</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|