TDSDUMP: Communication link failure

[ShiroiSkyy]

These errors occurred during the query, and these are the only ones. Please help me identify what the issue is.

TDS 5 -> SYBASE 12.0
PHP: PDO_ODBC

09:45:17.815 668 (odbc_export.h:1026):SQLGetConnectAttr(000002C965FF8CD0, 1209, 000000D2163FB734, 0, 000000D2163FB480)
09:45:17.815 668 (odbc.c:5067):odbc_SQLGetConnectAttr(000002C965FF8CD0, 1209, 000000D2163FB734, 0, 000000D2163FB480)
09:45:17.815 668 (odbc.c:6187):SQLGetInfo(000002C965FF8CD0, 25, 000002C9684C05E0, 128, 000000D2163FB730)
09:45:17.815 668 (odbc.c:5422):odbc_SQLGetInfo(000002C965FF8CD0, 25, 000002C9684C05E0, 128, 000000D2163FB730)
09:45:17.817 668 (odbc.c:1686):SQLAllocHandle(3, 000002C965FF8CD0, 000002C9684D26A8)
09:45:17.817 668 (odbc.c:1866):odbc_SQLAllocStmt(000002C965FF8CD0, 000002C9684D26A8)
09:45:17.817 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10010, 000002C9684D28E0, -4, 0000000000000000)
09:45:17.817 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10011, 000002C9684D29E8, -4, 0000000000000000)
09:45:17.817 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10012, 000002C9684D2AF0, -4, 0000000000000000)
09:45:17.817 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10013, 000002C9684D2BF8, -4, 0000000000000000)
09:45:17.817 668 (odbc_export.h:851):SQLPrepare(000002C965FF0210, Select 1 , 8)
09:45:17.817 668 (odbc.c:4840):Creating prepared statement
09:45:17.817 668 (mem.c:666):tds_free_all_results()
09:45:17.817 668 (util.c:179):Changed query state from IDLE to WRITING
09:45:17.817 668 (iconv.c:643):Converting from ISO-8859-1 to ISO-8859-1
09:45:17.817 668 (iconv.c:644):Conversion direction: to_server
09:45:17.817 668 (iconv.c:645):Client charset: ISO-8859-1
09:45:17.817 668 (iconv.c:646):Server charset: ISO-8859-1
09:45:17.817 668 (iconv.c:643):Converting from ISO-8859-1 to ISO-8859-1
09:45:17.817 668 (iconv.c:644):Conversion direction: to_server
09:45:17.817 668 (iconv.c:645):Client charset: ISO-8859-1
09:45:17.817 668 (iconv.c:646):Server charset: ISO-8859-1
09:45:17.817 668 (iconv.c:643):Converting from ISO-8859-1 to ISO-8859-1
09:45:17.817 668 (iconv.c:644):Conversion direction: to_server
09:45:17.817 668 (iconv.c:645):Client charset: ISO-8859-1
09:45:17.817 668 (iconv.c:646):Server charset: ISO-8859-1
09:45:17.817 668 (util.c:179):Changed query state from WRITING to DEAD
09:45:17.817 668 (packet.c:446):Write attempt when state is TDS_DEAD
09:45:17.817 668 (util.c:83):logic error: cannot change query state from DEAD to PENDING
09:45:17.817 668 (util.c:179):Changed query state from DEAD to DEAD
09:45:17.817 668 (util.c:118):logic error: cannot change query state from DEAD to IDLE
09:45:17.817 668 (util.c:179):Changed query state from DEAD to DEAD
09:45:17.817 668 (mem.c:226):tds_dynamic_deallocated() : freeing dynamic_id qwao634900
09:45:17.817 668 (error.c:417):odbc_errs_add: "Unknown error"
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 4, 000002C9637A7F40, 12, 000000D2163FB170)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 2, 4, 000002C9637A7F40, 12, 000000D2163FB170)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 4, 000002C9637A7EE0, 12, 000000D2163FB280)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 2, 4, 000002C9637A7DE0, 12, 000000D2163FB280)
09:45:17.818 668 (error_export.h:43):SQLGetDiagRec(3, 000002C965FF0210, 1, 000000D2163FB208, 0000000000000000, 0000000000000000, 0, 000000D2163FB338)
09:45:17.818 668 (error.c:563):SQLGetDiagRec: "[FreeTDS][SQL Server]Unknown error"
09:45:17.818 668 (error_export.h:43):SQLGetDiagRec(3, 000002C965FF0210, 1, 000000D2163FB208, 000000D2163FB308, 000002C9684C4AC0, 36, 000000D2163FB338)
09:45:17.818 668 (error.c:563):SQLGetDiagRec: "[FreeTDS][SQL Server]Unknown error"
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 8, 000002C9684C1EF0, 256, 000000D2163FB2D0)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 9, 000002C9684C2000, 256, 000000D2163FB2D0)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 10, 000002C9684C2220, 256, 000000D2163FB2D0)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 11, 000002C9684C2330, 256, 000000D2163FB2D0)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, -1248, 000000D2163FB348, 8, 000000D2163FB230)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, -1247, 000000D2163FB350, 4, 000000D2163FB230)
09:45:17.818 668 (error_export.h:43):SQLGetDiagRec(3, 000002C965FF0210, 2, 000000D2163FB208, 0000000000000000, 0000000000000000, 0, 000000D2163FB338)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 4, 000002C9637A7EE0, 12, 000000D2163FB3B0)
09:45:17.818 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 2, 4, 000002C9637A7EE0, 12, 000000D2163FB3B0)
09:45:17.818 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 5, 0000000000000000, -5)
09:45:17.818 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 5, 0000000000000000, -5)
09:45:17.818 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 27, 0000000000000001, -5)
09:45:17.818 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 27, 0000000000000001, -5)
09:45:17.818 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 26, 0000000000000000, -4)
09:45:17.818 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 26, 0000000000000000, -4)
09:45:17.818 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 23, 0000000000000000, -4)
09:45:17.818 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 23, 0000000000000000, -4)
09:45:17.818 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 25, 0000000000000000, -4)
09:45:17.818 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 25, 0000000000000000, -4)
09:45:17.818 668 (odbc.c:4302):SQLFreeHandle(3, 000002C965FF0210)
09:45:17.818 668 (odbc.c:4403):odbc_SQLFreeStmt(000002C965FF0210, 1, 0)
09:45:17.818 668 (odbc.c:1686):SQLAllocHandle(3, 000002C965FF8CD0, 000002C9684D26A8)
09:45:17.818 668 (odbc.c:1866):odbc_SQLAllocStmt(000002C965FF8CD0, 000002C9684D26A8)
09:45:17.818 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10010, 000002C9684D28E0, -4, 0000000000000000)
09:45:17.818 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10011, 000002C9684D29E8, -4, 0000000000000000)
09:45:17.818 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10012, 000002C9684D2AF0, -4, 0000000000000000)
09:45:17.818 668 (odbc.c:4739):SQLGetStmtAttr(000002C965FF0210, 10013, 000002C9684D2BF8, -4, 0000000000000000)
09:45:17.819 668 (odbc_export.h:815):SQLExecDirect(000002C965FF0210, SET ROWCOUNT 0, 14)
09:45:17.819 668 (prepare_query.c:209):parsing 0 parameters
09:45:17.819 668 (odbc.c:3484):odbc_SQLExecute(000002C965FF0210)
09:45:17.819 668 (odbc.c:3501):odbc_SQLExecute() starting with state 5
09:45:17.819 668 (error.c:417):odbc_errs_add: "Communication link failure"
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 4, 000002C9637A7F80, 12, 000000D2163FB1C0)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 2, 4, 000002C9637A8000, 12, 000000D2163FB1C0)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 4, 000002C9637A80C0, 12, 000000D2163FB2D0)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 2, 4, 000002C9637A7EE0, 12, 000000D2163FB2D0)
09:45:17.819 668 (error_export.h:43):SQLGetDiagRec(3, 000002C965FF0210, 1, 000000D2163FB258, 0000000000000000, 0000000000000000, 0, 000000D2163FB388)
09:45:17.819 668 (error.c:563):SQLGetDiagRec: "[FreeTDS][SQL Server]Communication link failure"
09:45:17.819 668 (error_export.h:43):SQLGetDiagRec(3, 000002C965FF0210, 1, 000000D2163FB258, 000000D2163FB358, 000002C9637A9630, 49, 000000D2163FB388)
09:45:17.819 668 (error.c:563):SQLGetDiagRec: "[FreeTDS][SQL Server]Communication link failure"
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 8, 000002C9684C2330, 256, 000000D2163FB320)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 9, 000002C9684C1DE0, 256, 000000D2163FB320)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 10, 000002C9684C1DE0, 256, 000000D2163FB320)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 11, 000002C9684C2000, 256, 000000D2163FB320)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, -1248, 000000D2163FB398, 8, 000000D2163FB280)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, -1247, 000000D2163FB3A0, 4, 000000D2163FB280)
09:45:17.819 668 (error_export.h:43):SQLGetDiagRec(3, 000002C965FF0210, 2, 000000D2163FB258, 0000000000000000, 0000000000000000, 0, 000000D2163FB388)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 1, 4, 000002C9637A7FC0, 12, 000000D2163FB400)
09:45:17.819 668 (error_export.h:176):SQLGetDiagField(3, 000002C965FF0210, 2, 4, 000002C9637A80A0, 12, 000000D2163FB400)
09:45:17.819 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 5, 0000000000000000, -5)
09:45:17.819 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 5, 0000000000000000, -5)
09:45:17.819 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 27, 0000000000000001, -5)
09:45:17.819 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 27, 0000000000000001, -5)
09:45:17.819 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 26, 0000000000000000, -4)
09:45:17.819 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 26, 0000000000000000, -4)
09:45:17.819 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 23, 0000000000000000, -4)
09:45:17.819 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 23, 0000000000000000, -4)
09:45:17.819 668 (odbc.c:7012):SQLSetStmtAttr(000002C965FF0210, 25, 0000000000000000, -4)
09:45:17.819 668 (odbc.c:6696):odbc_SQLSetStmtAttr(000002C965FF0210, 25, 0000000000000000, -4)
09:45:17.819 668 (odbc.c:4302):SQLFreeHandle(3, 000002C965FF0210)
09:45:17.819 668 (odbc.c:4403):odbc_SQLFreeStmt(000002C965FF0210, 1, 0)

[freddy77]

Hi. The first noticeable error from the log is

09:45:17.817 668 (util.c:179):Changed query state from WRITING to DEAD

this usually means that the server received something it didn't like and decided to close the connection. Usually I test Sybase 15 and 16 so it could be that FreeTDS is sending something "too new". Not idea why, the logs are not detailed enough. The query (Select 1) is surely pretty simple. It could also be that server closed the connection before even sending the query and the closure was detected later.

[ShiroiSkyy]

@freddy77
I've identified the issue: When using persistent connections via PHP PDO DSN to connect to the server, if network fluctuations occur or the server restarts, PHP remains unaware of the disconnection. When sending queries afterward, errors arise—even manually releasing PDO resources doesn't help. Reconnecting works, but queries still fail. Additionally, if problems occur, switching to non-persistent connections works temporarily, but that's not a fundamental solution. Can this be resolved at the FreeTDS driver level? Another observation: killing the PHP process also resolves the issue.

[freddy77]

I'm not entirely up to date with PHP. Do you have some code, at least doing the connection? Which PDO driver are you using?

[ShiroiSkyy]

try {
    $options = [
        PDO::ATTR_ERRMODE          => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_PERSISTENT       => true,
    ];
  
    $dsn2 = "sybase:host=192.1.1.13:5000;"
        . "dbname=pos;"
        . "charset=UTF-8;"
        . "appname=test2;";
  
    $pdo = new PDO($dsn2, 'sa', '', $options);
    $result = $pdo->query("select 1");
    print_r($result->fetchAll());
  
} catch (PDOException $e) {
    echo "failed: " . $e->getMessage();
}

The initial connection works fine. However, after restarting the remote Sybase 12 service and executing query(), the following error occurs:
"failed: SQLSTATE[HY000]: General error: 20047 DBPROCESS is dead or not enabled [20047] (severity 9) [select 1]"

If the appname is modified to reconnect, it works normally, but it cannot use the same name as the abnormal connection; otherwise, an error will be reported.
It is worth noting that the connection itself is normal, but query() cannot be executed, resulting in the error shown above.

When using the PDO_ODBC driver with FreeTDS, the issue cannot be reliably reproduced.

The example uses:

• Apache 2.4
• PHP 8.5.3
• PDO_DBLIB + FreeTDS (ct.dll + sybdb.dll placed in the PHP root directory)
• Windows

PDO_DBLIB: https://github.com/php/php-src/tree/PHP-8.5.3/ext/pdo_dblib

[freddy77]

From a quick look it looks like pdo_dblib driver does not detect if a DBPROCESS is still connected. It should not be hard to fix.
pdo_odbc and FreeTDS ODBC driver are able to do it.

[ShiroiSkyy]

I don't understand this code. Could you please advise how to fix it?

[freddy77]

Not tested but should work (please try it) freddy77/php-src@c08eec8.

[ShiroiSkyy]

Not tested but should work (please try it) freddy77/php-src@c08eec8.

Oh! It works fine now, and the issue has been resolved.

[freddy77]

PHP PR at php/php-src#21681.