Editing Flow-Diagrams (section)

== 8. Inter-Program Call Sequence — Report Run ==

'''What it shows:''' All CALL interactions during a <code>report</code> invocation — UI setup, database connection, transaction and cursor lifecycle, the fetch loop, and shutdown.

<pre class="mermaid">sequenceDiagram
    participant OS as OS / Shell
    participant main as primesmain
    participant gen as primesgen
    participant dal as primes (DAL)
    participant ui as primesui
    participant db as PostgreSQL
    participant prt as primes.prt

    OS-&gt;&gt;main: execute with arg &quot;report&quot;

    main-&gt;&gt;ui: CALL &quot;primesui&quot; ui-methods=&quot;start&quot;
    ui-&gt;&gt;prt: OPEN OUTPUT
    prt--&gt;&gt;ui: file-status=&quot;00&quot;
    ui--&gt;&gt;main: ui-method-result=0

    main-&gt;&gt;gen: CALL &quot;primesgen&quot; methods=&quot;report&quot;

    gen-&gt;&gt;dal: CALL &quot;primes&quot; dal-methods=&quot;connect&quot;
    dal-&gt;&gt;db: EXEC SQL CONNECT TO primes
    db--&gt;&gt;dal: SQLCODE=0
    dal--&gt;&gt;gen: dal-result=0
    gen-&gt;&gt;ui: LOG &quot;Database initialisation succeeded.&quot;

    gen-&gt;&gt;dal: CALL &quot;primes&quot; dal-methods=&quot;cursor&quot;
    dal-&gt;&gt;db: EXEC SQL AT primes START TRANSACTION
    dal-&gt;&gt;db: EXEC SQL OPEN primescursor
    db--&gt;&gt;dal: SQLCODE=0
    dal--&gt;&gt;gen: dal-result=0
    gen-&gt;&gt;ui: LOG &quot;Cursor initialisation succeeded.&quot;

    gen-&gt;&gt;dal: r94-fetch → dal-methods=&quot;next-prime&quot;
    dal-&gt;&gt;db: EXEC SQL FETCH primescursor INTO :primes-row
    db--&gt;&gt;dal: first row (ident, prime)
    dal--&gt;&gt;gen: primes-sequence, prime-number / dal-result=0
    gen-&gt;&gt;ui: LOG &quot;Fetch first row ok.&quot;

    loop for each row until cursor exhausted
        gen-&gt;&gt;ui: CALL &quot;primesui&quot; ui-methods=&quot;write&quot; u-sequence / u-number
        ui-&gt;&gt;prt: accumulate in 6-col buffer\nwrite 132-char line every 6 entries\nwrite heading+footing at page boundaries
        gen-&gt;&gt;dal: r94-fetch → dal-methods=&quot;next-prime&quot;
        dal-&gt;&gt;db: EXEC SQL FETCH primescursor
        db--&gt;&gt;dal: next row or SQLCODE≠0 (no more rows)
        dal--&gt;&gt;gen: dal-result=0 (row) or dal-result=1 (eof/error)
        note over gen: ⚠️ session-method-eof (9) never set;\nloop exits on error (1), not clean eof
    end

    gen-&gt;&gt;dal: CALL &quot;primes&quot; dal-methods=&quot;disconnect&quot;
    dal-&gt;&gt;db: EXEC SQL CONNECT RESET primes
    db--&gt;&gt;dal: SQLCODE=0
    dal--&gt;&gt;gen: dal-result=0
    gen--&gt;&gt;main: session-result=0 / EXIT PROGRAM

    main-&gt;&gt;ui: CALL &quot;primesui&quot; ui-methods=&quot;log-message&quot; &quot;Primes run complete.&quot;
    main-&gt;&gt;ui: CALL &quot;primesui&quot; ui-methods=&quot;stop&quot;
    ui-&gt;&gt;ui: pad remaining cells with zeros\nPERFORM r92 UNTIL new-page\nCLOSE fprinter
    ui-&gt;&gt;prt: CLOSE
    prt--&gt;&gt;ui: file-status=&quot;00&quot;
    ui--&gt;&gt;main: ui-method-result=0
    main-&gt;&gt;OS: STOP RUN</pre>

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