SQL Server

Flush an SFTP File to Stable Storage (Fsync)

Demonstrates the Chilkat SFtp.Fsync method, which requests that the server flush pending data for an open file to stable storage. The only argument is the handle. It uses the OpenSSH fsync@openssh.com extension and succeeds only when the server supports it.

Background: A successful write does not guarantee the data has reached disk — it may still sit in the server's write cache, where a crash or power loss would lose it. Fsync forces it to durable storage, which matters for transactional or journal-style files where a committed record must survive a failure. Because it relies on a non-standard OpenSSH extension, expect it to fail against servers that do not implement it, and treat that as a capability check rather than a hard error where appropriate.

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-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    --  Demonstrates the SFtp.Fsync method, which requests that the server flush pending data for an
    --  open file to stable storage.  The only argument is the handle.

    DECLARE @sftp int
    EXEC @hr = sp_OACreate 'Chilkat.SFtp', @sftp OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    --  Connect, authenticate, and initialize the SFTP subsystem.
    DECLARE @port int
    SELECT @port = 22
    EXEC sp_OAMethod @sftp, 'Connect', @success OUT, 'sftp.example.com', @port
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @sftp, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sftp
        RETURN
      END

    --  Normally you would not hard-code the password in source.  You should instead obtain it
    --  from an interactive prompt, environment variable, or a secrets vault.
    DECLARE @password nvarchar(4000)
    SELECT @password = 'mySshPassword'

    EXEC sp_OAMethod @sftp, 'AuthenticatePw', @success OUT, 'mySshLogin', @password
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @sftp, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sftp
        RETURN
      END

    EXEC sp_OAMethod @sftp, 'InitializeSftp', @success OUT
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @sftp, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sftp
        RETURN
      END

    DECLARE @handle nvarchar(4000)
    EXEC sp_OAMethod @sftp, 'OpenFile', @handle OUT, 'subdir/journal.log', 'writeOnly', 'openOrCreate,appendData'
    EXEC sp_OAGetProperty @sftp, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 = 0
      BEGIN
        EXEC sp_OAGetProperty @sftp, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sftp
        RETURN
      END

    --  Write a critical record.
    EXEC sp_OAMethod @sftp, 'WriteFileText', @success OUT, @handle, 'utf-8', '2026-07-23 transaction committed' + CHAR(10)
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @sftp, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sftp
        RETURN
      END

    --  Ask the server to flush the data to durable storage before continuing.  Fsync uses the
    --  OpenSSH fsync@openssh.com extension and succeeds only when the server supports it.
    EXEC sp_OAMethod @sftp, 'Fsync', @success OUT, @handle
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @sftp, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sftp
        RETURN
      END

    EXEC sp_OAMethod @sftp, 'CloseHandle', @success OUT, @handle
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @sftp, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sftp
        RETURN
      END

    PRINT 'Data flushed to stable storage.'

    EXEC sp_OAMethod @sftp, 'Disconnect', NULL

    EXEC @hr = sp_OADestroy @sftp


END
GO