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# Run this Tcl script to generate the pragma.html file.
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set rcsid {$Id: pragma.tcl,v 1.20 2007/02/02 12:33:17 drh Exp $}
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set rcsid {$Id: pragma.tcl,v 1.22 2007/04/02 00:53:19 drh Exp $}
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header {Pragma statements supported by SQLite}
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Unknown pragmas are simply ignored. This means if there is a typo in
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a pragma statement the library does not inform the user of the fact.
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<li>Some pragmas take effect during the SQL compilation stage, not the
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execution stage. This means if using the C-language sqlite3_compile(),
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execution stage. This means if using the C-language sqlite3_prepare(),
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sqlite3_step(), sqlite3_finalize() API (or similar in a wrapper
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interface), the pragma may be applied to the library during the
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sqlite3_compile() call.
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sqlite3_prepare() call.
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<li>The pragma command is unlikely to be compatible with any other SQL
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<p>The available pragmas fall into four basic categories:</p>
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<li>Pragmas used to <a href="#schema">query the schema</a> of the current
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<li>Pragmas used to <a href="#modify">modify the operation</a> of the
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SQLite library in some manner, or to query for the current mode of
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<li>Pragmas used to <a href="#schema">query the schema</a> of the current
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<li>Pragmas used to <a href="#version">query or modify the databases two
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version values</a>, the schema-version and the user-version.
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<li>Pragmas used to <a href="#debug">debug the library</a> and verify that
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effect on databases that already exist.</p>
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<a name="pragma_locking_mode"></a>
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<li><p><b>PRAGMA locking_mode;
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<br>PRAGMA locking_mode = <i>NORMAL | EXCLUSIVE</i></b></p>
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<p>This pragma sets or queries the database connection locking-mode.
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The locking-mode is either NORMAL or EXCLUSIVE.
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<p>In NORMAL locking-mode (the default), a database connection
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unlocks the database file at the conclusion of each read or
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write transaction. When the locking-mode is set to EXCLUSIVE, the
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database connection never releases file-locks. The first time the
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database is read in EXCLUSIVE mode, a shared lock is obtained and
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held. The first time the database is written, an exclusive lock is
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obtained and held.</p>
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<p>Database locks obtained by a connection in EXCLUSIVE mode may be
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released either by closing the database connection, or by setting the
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locking-mode back to NORMAL using this pragma and then accessing the
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database file (for read or write). Simply setting the locking-mode to
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NORMAL is not enough - locks are not be released until the next time
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the database file is accessed.</p>
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<p>There are two reasons to set the locking-mode to EXCLUSIVE. One
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is if the application actually wants to prevent other processes from
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accessing the database file. The other is that a small number of
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filesystem operations are saved by optimizations enabled in this
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mode. This may be significant in embedded environments.</p>
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<p>When the locking_mode pragma specifies a particular database,
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PRAGMA <b>main.</b>locking_mode=EXCLUSIVE;
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<p>Then the locking mode applies only to the named database. If no
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database name qualifier preceeds the "locking_mode" keyword then
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the locking mode is applied to all databases, including any new
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databases added by subsequent <a href="lang_attach.html">ATTACH</a>
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<p>The "temp" database (in which TEMP tables and indices are stored)
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always uses exclusive locking mode. The locking mode of temp cannot
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be changed. All other databases use the normal locking mode by default
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and are effected by this pragma.</p>
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<a name="pragma_page_size"></a>
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<li><p><b>PRAGMA page_size;
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