LabVIEW VI Caching on Network Drives with Unchanging Timestamps

Answer the Question First

LabVIEW’s cache is timestamp‑based. On a network drive that does not update timestamps reliably, a VI can appear stale. The following options let you force a recompilation for a single VI while leaving the global cache enabled.

• VI Properties → Execution → Disable Caching – toggles a flag for that VI only.
• VI Server – Set CacheEnabled = false – programmatic equivalent.
• VI Server – FlushCache – removes the cached compiled code for a specific VI reference.

No built‑in checksum‑based invalidation exists; the mechanism always relies on file timestamps. The only alternative is to manually clear the cache for the affected VI after editing.

Why Timestamps Fail on Network Drives

SMB and other network file systems often delay or suppress last‑modified updates, especially when opportunistic locking is enabled. This leads LabVIEW to think the VI hasn’t changed.

Step‑by‑Step Guidance

1. Open the VI in question. Go to File → VI Properties → Execution and check Disable caching. This setting is stored in the VI’s metadata and is respected only for this VI.

2. Save and close the VI. Re‑open it; the next run will load the source from disk and recompile, regardless of the timestamp.

3. Programmatic alternative:

   viRef = VI.Server.Application.Reference.GetVIReference("\\network\path\my.vi");
   viRef.CacheEnabled = false;   // disables caching for this reference only
   viRef.FlushCache();            // removes any existing compiled code
   

   After the FlushCache call, the next execution will recompile the VI.

4. Verify the change. Add a visible indicator or use Probe to confirm that the updated block diagram is executed.

Checksum‑Based Invalidation – Not Available

LabVIEW does not expose a setting to switch from timestamp checks to checksum or hash comparisons. The caching algorithm is hard‑coded to use the file’s last‑modified time.

When to Use These Options

• During active development on a shared network drive where the timestamp may not propagate.
• When a single VI is known to be edited frequently, but you want to keep the rest of the application cached for performance.
• When you cannot afford a full application restart or global cache flush.

Additional Considerations

Disabling caching for a VI increases execution time, especially for large block diagrams or tight loops. Use the property only for VIs that are edited often. After the VI is stable, re‑enable caching to regain performance.

Because the cache is per‑application, any changes to the VI file on disk while the VI is running will not be seen until the VI is closed or the cache is flushed.

Diagnostic Question

If you notice that the VI still runs old code after clearing the cache, check whether File → VI Properties → Execution → Disable caching is still unchecked and whether the VI is currently open in another LabVIEW instance. Resolving that will typically restore the expected behavior.