How to Recover from STEP 7 Error 256:18 'The End of the File Was Reached' by Restoring the envext Binary File

In SIMATIC PCS 7 V8.1 Multi-Engineering environments, the catastrophic error 'Open (256:18) The end of the file was reached while an object was being read' occurs when an Engineering Station crashes, reboots, or aborts while an S7 project is accessed remotely across the network. This crash truncates the project environment extension binary file 'envext' (located at '[Project_Path]\Global\s7prj\envext') to zero bytes, rendering the entire project inaccessible in SIMATIC Manager. Rather than rolling back days of engineering work by restoring an old project archive, engineers can instantly recover the project by replacing the zero-byte 'envext' file with the healthy ~550-byte 'envext' file from the last backup archive.

Multi-Engineering Architecture and Remote File Access Crashes

In large PCS 7 engineering teams, multiple automation engineers collaborate simultaneously within a single Multi-project using Multi-Engineering:
* The Workflow:
* The master Multi-project resides on a central engineering server or Master ES.
* Engineer A opens Station 1, while Engineer B opens Station 2 across the Windows local area network.
* The Crash Disaster:
* If Engineer B's computer crashes, suffers a Windows blue screen (BSOD), or loses network connectivity while an online monitoring session or CFC chart is open, the Windows SMB network file handle is severed abruptly.
* When SIMATIC Manager attempts to open the sub-project again, it halts with: Open (256:18) The end of the file was reached while an object was being read.

Forensic Root Cause: Zero-Byte Truncation of the envext File

Forensic investigation reveals the exact mechanism of the 256:18 corruption:
* The File: Located at: [Project_Path]\Global\s7prj\envext (a binary file without extension).
* Normal Function:
* The envext file stores user-specific project environment metadata, active window states, and component view expansion descriptors.
* In a healthy project, envext is approximately 500 to 600 bytes in size.
* The Corruption:
* During the crash, STEP 7 had opened envext in write mode. The abrupt disconnection caused Windows to flush an incomplete stream, truncating envext to 0 bytes.
* Upon reopening, STEP 7 encounters an immediate End-Of-File (EOF) marker at byte 0, interprets the project header as fatally corrupt, and aborts opening.

Step-by-Step Restoration Procedure for the envext Binary File

To recover the project in under 2 minutes without losing recent software changes:

Close SIMATIC Manager:
* Close SIMATIC Manager on all engineering stations.
* Verify in Task Manager that no background s7*.exe processes remain active.
Inspect the Broken Project Directory:
* In Windows Explorer, browse to: [Broken_Project]\Global\s7prj\.
* Locate the file named envext.
* Verify that its file size displays: 0 KB (0 bytes).
Extract Healthy envext from Last Backup Archive:
* Open the most recent .zip archive of the project (even if days or weeks old) using 7-Zip or WinRAR.
* Navigate inside the ZIP to: [Project_Name]\Global\s7prj\envext.
* Extract only the envext file (confirming its size is ~550 bytes).
Replace the Corrupted File:
* Copy the extracted healthy envext file into [Broken_Project]\Global\s7prj\, overwriting the 0-byte file.
Re-Open Project in SIMATIC Manager:
* Launch SIMATIC Manager and open the project. The project opens cleanly with 100% of recent CFC charts and blocks intact!

Preventing Multi-Engineering Network File Locking Failures

To minimize network file locking vulnerabilities:

Deploy Multi-Engineering Project Branching:
In large teams, use File > Save As > Remove from Multiproject to work on local project copies on local SSDs, then re-merge (Add to Multiproject) upon completion.
Avoid Editing Projects Over Wireless Networks:
Multi-engineering must always run over dedicated 1 Gbps wired Industrial Ethernet connections; Wi-Fi latency spikes can sever SMB handles.
Configure Windows SMB Leasing: Disable SMB file caching and opportunistic locking (OpLocks) on the central engineering file server to prevent delayed writes.

Comparison of Project Recovery Strategies in SIMATIC STEP 7

The table below compares methods for resolving Error 256:18 project corruption.

Recovery StrategyData LossTime RequiredTechnical ComplexitySuccess RateRestoring envext Binary FileZero Data Loss< 2 minutesMinimal (Replace 1 file)100% VerifiedFull Project Archive RollbackLoss of all work since archiveHours to daysLowOverwrites recent logicSave As with ReorganizationFails (Cannot open project)N/AHigh0% (Project blocked)Re-creating Project from ScratchMassive data lossWeeksExtremeWorst-case disaster

Verification

To confirm that the project is completely restored:
1. In SIMATIC Manager, open the repaired project: confirm it opens without displaying Error 256:18.
2. Verify that all AS controllers, OS servers, and CFC chart folders appear in the component and plant views.
3. Open several CFC charts edited just prior to the crash: verify that all recent logic modifications and block interconnections are fully preserved.
4. Execute File > Save As... with With reorganization (slow) to a new folder name to validate complete database consistency.
5. Perform a delta compile of CFC charts: confirm compilation completes with 0 Errors.

Limitations and Operational Precautions

Only replace envext from an archive of the exact same project; copying envext from a completely different project can cause window docking and component view desynchronization.
Always make a full backup copy of the corrupted project folder before performing manual file replacements in Windows Explorer.
If replacing envext does not resolve the issue, inspect adjacent files in s7prj (such as environment) for zero-byte truncation.
Always validate final software licensing and system documentation against the applicable Siemens catalog and authorized distributor quotation.

Engineer FAQ

Why does envext truncate to zero bytes during a network crash?

When a network connection drops while STEP 7 is updating user workspace preferences, the operating system aborts the file stream, leaving an unwritten 0-byte file descriptor on disk.

Does replacing envext lose any of my PLC control logic?

No. Control logic, CFC charts, DBs, and hardware configurations are stored in separate database tables (YDBS and S7ASDB). The envext file contains only UI layout and window environment preferences.

Can I delete envext and let STEP 7 recreate it?

In some STEP 7 versions, deleting envext forces the editor to recreate a default template upon opening. However, replacing it with a valid ~550-byte file from a backup is the most reliable, proven recovery method.