2011-09-13 17:44:24 +00:00
<?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 > Enabling Transaction Snapshots in the SQL Layer< / 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 = "Berkeley DB Installation and Build Guide" / >
< link rel = "up" href = "upgrade_52_toc.html" title = "Chapter / >
< link rel = "prev" href = "upgrade_11gr2_52_heap.html" title = "Heap Access Method" / >
< link rel = "next" href = "upgrade_11gr2_52_rep_2site_strict.html" title = "2SITE_STRICT Enabled by Default in Replication" / >
< / head >
< body >
< div xmlns = "" class = "navheader" >
< div class = "libver" >
< p > Library Version 11.2.5.2< / p >
< / div >
< table width = "100%" summary = "Navigation header" >
< tr >
< th colspan = "3" align = "center" > Enabling Transaction Snapshots in the SQL Layer< / th >
< / tr >
< tr >
< td width = "20%" align = "left" > < a accesskey = "p" href = "upgrade_11gr2_52_heap.html" > Prev< / a > < / td >
< th width = "60%" align = "center" > Chapter
Upgrading Berkeley DB 11.2.5.1 applications to Berkeley DB 11.2.5.2
< / th >
< td width = "20%" align = "right" > < a accesskey = "n" href = "upgrade_11gr2_52_rep_2site_strict.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 = "upgrade_11gr2_52_mvcc_sql" > < / a > Enabling Transaction Snapshots in the SQL Layer< / h2 >
< / div >
< / div >
< / div >
< div class = "toc" >
< dl >
< dt >
< span class = "sect2" >
2011-12-20 00:07:10 +00:00
< a href = "upgrade_11gr2_52_mvcc_sql.html#id3647237" > New Pragmas< / a >
2011-09-13 17:44:24 +00:00
< / span >
< / dt >
< / dl >
< / div >
< p >
Read/write concurrency can now be enabled in the SQL API by using
< code class = "literal" > PRAGMA multiversion=on< / code > before accessing any
tables in the database. After multiversion has been enabled, it
can be temporarily disabled using the
< code class = "literal" > PRAGMA transaction_snapshots=on/off< / code > .
< / p >
< div class = "sect2" lang = "en" xml:lang = "en" >
< div class = "titlepage" >
< div >
< div >
2011-12-20 00:07:10 +00:00
< h3 class = "title" > < a id = "id3647237" > < / a > New Pragmas< / h3 >
2011-09-13 17:44:24 +00:00
< / div >
< / div >
< / div >
< p >
For more details on pragmas concerning Transaction Snapshots
read < a href = "../bdb-sql/mvcc.html" class = "olink" > Using Multiversion Concurrency Control< / a > in the < em class = "citetitle" > Berkeley DB Getting Started with the SQL APIs< / em > guide.
< / p >
< div class = "itemizedlist" >
< ul type = "disc" >
< li >
< code class = "literal" > PRAGMA multiversion=ON|OFF;< / code >
< / li >
< li >
< code class = "literal" > PRAGMA snapshot_isolation=ON|OFF< / code >
< / li >
< / ul >
< / div >
< / div >
< / div >
< div class = "navfooter" >
< hr / >
< table width = "100%" summary = "Navigation footer" >
< tr >
< td width = "40%" align = "left" > < a accesskey = "p" href = "upgrade_11gr2_52_heap.html" > Prev< / a > < / td >
< td width = "20%" align = "center" >
< a accesskey = "u" href = "upgrade_52_toc.html" > Up< / a >
< / td >
< td width = "40%" align = "right" > < a accesskey = "n" href = "upgrade_11gr2_52_rep_2site_strict.html" > Next< / a > < / td >
< / tr >
< tr >
< td width = "40%" align = "left" valign = "top" > Heap Access Method < / td >
< td width = "20%" align = "center" >
< a accesskey = "h" href = "index.html" > Home< / a >
< / td >
< td width = "40%" align = "right" valign = "top" > < / td >
< / tr >
< / table >
< / div >
< / body >
< / html >
