SQLite

#
# Run this Tcl script to generate the pragma.html file.
#
set rcsid {$Id: pragma.tcl,v 1.21 2007/03/26 08:41:13 danielk1977 Exp $}
source common.tcl
header {Pragma statements supported by SQLite}

proc Section {name {label {}}} {
  puts "\n<hr />"
  if {$label!=""} {
    puts "<a name=\"$label\"></a>"

<ul>
<li>Specific pragma statements may be removed and others added in future
    releases of SQLite. Use with caution!
<li>No error messages are generated if an unknown pragma is issued.
    Unknown pragmas are simply ignored. This means if there is a typo in 
    a pragma statement the library does not inform the user of the fact.
<li>Some pragmas take effect during the SQL compilation stage, not the
    execution stage. This means if using the C-language sqlite3_prepare(), 
    sqlite3_step(), sqlite3_finalize() API (or similar in a wrapper 
    interface), the pragma may be applied to the library during the 
    sqlite3_prepare() call.
<li>The pragma command is unlikely to be compatible with any other SQL
    engine.
</ul>

<p>The available pragmas fall into four basic categories:</p>
<ul>


<li>Pragmas used to <a href="#modify">modify the operation</a> of the 
    SQLite library in some manner, or to query for the current mode of 
    operation.
<li>Pragmas used to <a href="#schema">query the schema</a> of the current 
    database.
<li>Pragmas used to <a href="#version">query or modify the databases two 
    version values</a>, the schema-version and the user-version.
<li>Pragmas used to <a href="#debug">debug the library</a> and verify that
    database files are not corrupted.
</ul>
}

    are created using the latest file format which might not be
    readable or writable by older versions of SQLite.</p>

    <p>This flag only affects newly created databases.  It has no
    effect on databases that already exist.</p>
</li>

<a name="pragma_locking_mode"></a>
<li><p><b>PRAGMA locking_mode;
       <br>PRAGMA locking_mode = <i>NORMAL | EXCLUSIVE</i></b></p>
    <p>This pragma sets or queries the database connection locking-mode. 
    The locking-mode is either NORMAL or EXCLUSIVE.

    <p>In NORMAL locking-mode (the default), a database connection
    unlocks the database file at the conclusion of each read or
    write transaction. When the locking-mode is set to EXCLUSIVE, the
    database connection never releases file-locks. The first time the
    database is read in EXCLUSIVE mode, a shared lock is obtained and 
    held. The first time the database is written, an exclusive lock is
    obtained and held.

    <p>Database locks obtained by a connection in EXCLUSIVE mode may be
    released either by closing the database connection, or by setting the
    locking-mode back to NORMAL using this pragma and then accessing the
    database file (for read or write). Simply setting the locking-mode to
    NORMAL is not enough, locks not be released until the next time
    the database file is accessed.

    <p>There are two reasons to set the locking-mode to EXCLUSIVE. One
    is if the application actually wants to prevent other processes from
    accessing the database file. The other is that a small number of
    filesystem operations are saved by optimizations enabled in this
    mode. This may be significant in embedded environments.
</li>

<a name="pragma_page_size"></a>
<li><p><b>PRAGMA page_size;
       <br>PRAGMA page_size = </b><i>bytes</i><b>;</b></p>
    <p>Query or set the page-size of the database. The page-size
    may only be set if the database has not yet been created. The page
    size must be a power of two greater than or equal to 512 and less