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38        <span>In addition to exceptions, the</span>
39        
40        DB interfaces always return a value of 0 on success. If the
41        operation does not succeed for any reason, the return value will be
42        non-zero.
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45        If a system error occurred (for example, DB ran out of disk
46        space, or permission to access a file was denied, or an illegal argument
47        was specified to one of the interfaces), DB returns an
48        <tt class="literal">errno</tt>
49        value. All of the possible values of <tt class="literal">errno</tt> are greater than 0.
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52        If the operation did not fail due to a system error, but was not
53        successful either, DB returns a special error value. For
54        example, if you tried to retrieve data from the database and the
55        record for which you are searching does not exist, DB would return
56        <tt class="literal">DB_NOTFOUND</tt>, a special error value that means the requested
57        key does not appear in the database. All of the possible special error
58        values are less than 0.
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