Global / Local Memory
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Global and Local Memory connections store tag values entirely within the application’s own memory — no physical device or network communication required. They serve as a virtual PLC, useful for auxiliary variables, cross-tag communication, and test or demo projects.
Global Memory
Global Memory is stored on the server. All clients connected to the same DataTalk instance share the same values — if one client writes a value, every other client sees the updated value immediately.
Use cases:
- Setpoints or parameters entered by an operator that must be visible to all HMI clients
- Shared counters or accumulators
- Intermediate calculation results used across multiple dashboards or scripts
- Demo projects without physical hardware
Local Memory
Local Memory is stored in the client’s browser cache. Values are local to each browser session — other clients do not see them. Clearing the browser cache or opening an incognito window resets all Local Memory values to their initialization values.
Use cases:
- Per-client temporary variables
- Shift totals that reset on a new session
- Scratchpad values in scripted calculations visible only to one operator
Supported data types
| Category | Examples |
|---|---|
| Number | Int, Float, Bool, Date, … |
| String | String |
| UDT | User-Defined Data Type |
Persistence
Each Global or Local Memory tag has a Persistent option. When enabled, the tag retains its last value after the server restarts. When disabled, the tag resets to its initialization value on every restart.