1<!--$Id: qnx.so,v 11.12 2008/01/07 02:29:19 david Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB Reference Guide: QNX</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<a name="2"><!--meow--></a> 12<table width="100%"><tr valign=top> 13<td><b><dl><dt>Berkeley DB Reference Guide:<dd>Building Berkeley DB for UNIX/POSIX systems</dl></b></td> 14<td align=right><a href="/build_unix/osf1.html"><img src="/images/prev.gif" alt="Prev"></a><a href="/toc.html"><img src="/images/ref.gif" alt="Ref"></a><a href="/build_unix/sco.html"><img src="/images/next.gif" alt="Next"></a> 15</td></tr></table> 16<p align=center><b>QNX</b></p> 17<ol> 18<p><li><b>To what versions of QNX has DB been ported?</b> 19<p>Berkeley DB has been ported to the QNX Neutrino technology which is commonly 20referred to as QNX RTP (Real-Time Platform). Berkeley DB has not been 21ported to earlier versions of QNX, such as QNX 4.25.</p> 22<p><li><b>Building Berkeley DB shared libraries fails.</b> 23<p>The <b>/bin/sh</b> utility distributed with some QNX releases drops 24core when running the GNU libtool script (which is used to build Berkeley DB 25shared libraries). There are two workarounds for this problem: First, 26only build static libraries. You can disable building shared libraries 27by specifying the <a name="--disable-shared">--disable-shared</a> configuration flag when 28configuring Berkeley DB.</p> 29<p>Second, build Berkeley DB using an alternate shell. QNX distributions include 30an accessories disk with additional tools. One of the included tools 31is the GNU bash shell, which is able to run the libtool script. To 32build Berkeley DB using an alternate shell, move <b>/bin/sh</b> aside, link 33or copy the alternate shell into that location, configure, build and 34install Berkeley DB, and then replace the original shell utility.</p> 35<p><li><b>Are there any QNX filesystem issues?</b> 36<p>Berkeley DB generates temporary files for use in transactionally 37protected file system operations. Due to the filename length limit of 3848 characters in the QNX filesystem, applications that are using 39transactions should specify a database name that is at most 43 characters.</p> 40<p><li><b>What are the implications of QNX's requirement to use 41<b>shm_open</b>(2) in order to use <b>mmap</b>(2)?</b> 42<p>QNX requires that files mapped with <b>mmap</b>(2) be opened using 43<b>shm_open</b>(2). There are other places in addition to the 44environment shared memory regions, where Berkeley DB tries to memory map files 45if it can.</p> 46<p>The memory pool subsystem normally attempts to use <b>mmap</b>(2) 47even when using private memory, as indicated by the <a href="/api_c/env_open.html#DB_PRIVATE">DB_PRIVATE</a> 48flag to <a href="/api_c/env_open.html">DB_ENV->open</a>. In the case of QNX, if an application is 49using private memory, Berkeley DB will not attempt to map the memory and will 50instead use the local cache.</p> 51<p><li><b>What are the implications of QNX's mutex implementation using 52microkernel resources?</b> 53<p>On QNX, the primitives implementing mutexes consume system resources. 54Therefore, if an application unexpectedly fails, those resources could 55leak. Berkeley DB solves this problem by always allocating mutexes in the 56persistent shared memory regions. Then, if an application fails, 57running recovery or explicitly removing the database environment by 58calling the <a href="/api_c/env_remove.html">DB_ENV->remove</a> method will allow Berkeley DB to release those 59previously held mutex resources. If an application specifies the 60<a href="/api_c/env_open.html#DB_PRIVATE">DB_PRIVATE</a> flag (choosing not to use persistent shared memory), 61and then fails, mutexes allocated in that private memory may leak their 62underlying system resources. Therefore, the <a href="/api_c/env_open.html#DB_PRIVATE">DB_PRIVATE</a> flag 63should be used with caution on QNX.</p> 64</ol> 65<table width="100%"><tr><td><br></td><td align=right><a href="/build_unix/osf1.html"><img src="/images/prev.gif" alt="Prev"></a><a href="/toc.html"><img src="/images/ref.gif" alt="Ref"></a><a href="/build_unix/sco.html"><img src="/images/next.gif" alt="Next"></a> 66</td></tr></table> 67<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 68</body> 69</html> 70
