Editing Flow-Diagrams (section)

== 4. Prime Report — Cursor Loop ==

'''Program:''' <code>primesgen.cbl</code> (r86, r90, r94) + <code>primes.cbl</code> (s01, s02)<br />
'''What it shows:''' How the report path opens a cursor over the database, fetches rows one at a time, and sends each to the print buffer.

<pre class="mermaid">flowchart TD
    A([r90-start-primes-report]) --&gt; B[CALL primes 'connect'\ndal-methods = 'connect']
    B --&gt; C{dal-method-ok?}
    C --&gt;|No| FAIL1([LOG 'Database init failed.'\nsession-result = 1\nGOTO close])
    C --&gt;|Yes| D[LOG 'Database initialisation succeeded.'\nCALL primes 'cursor'\ndal-methods = 'cursor']

    D --&gt; E[s01-cursor:\nEXEC SQL START TRANSACTION\nEXEC SQL OPEN primescursor]
    E --&gt; F{dal-method-ok?}
    F --&gt;|No| FAIL2([LOG 'Cursor init failed.'\nsession-result = 1\nGOTO close])
    F --&gt;|Yes| G[LOG 'Cursor initialisation succeeded.'\nr94-fetch → CALL primes 'next-prime'\nFETCH primescursor INTO primes-row]

    G --&gt; H{dal-method-ok?}
    H --&gt;|No| FAIL3([LOG 'Fetch first row nok.'\ndal-result = 1\nGOTO close])
    H --&gt;|Yes| I[LOG 'Fetch first row ok.'\ndal-result = 0]

    I --&gt; LOOP{session-method-eof?}
    LOOP --&gt;|Yes| CLOSE[r99-close-primes\nCALL primes 'disconnect']
    CLOSE --&gt; END([EXIT PROGRAM])

    LOOP --&gt;|No| WRITE[r86-report-primes\nMOVE primes-data TO u-primes\nCALL primesui 'write']
    WRITE --&gt; FETCH[r94-fetch\nCALL primes 'next-prime'\nFETCH primescursor INTO primes-row]
    FETCH --&gt; FCHECK{dal-method-ok?}
    FCHECK --&gt;|Yes| LOOP
    FCHECK --&gt;|No| ERR[LOG 'Fetch failed.'\nsession-result = 1]
    ERR --&gt; LOOP</pre>
<blockquote>⚠️ <code>session-result = 1</code> (nok) is set on fetch failure, but the loop condition tests <code>session-method-eof</code> (value 9). These values do not match — the loop will continue rather than exit cleanly on cursor exhaustion. See [[Technical-Specification#7-known-technical-issues|Technical Specification — Defect T7]].
</blockquote>

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<span id="dal-primes.cbl-method-dispatch"></span>