---
name: high-availability
description: >-
  CI Server R1.03 high availability with HAC (redundant servers). Use when the user asks about
  redundant / dual / triple / quad servers, primary and secondary server, active and standby,
  switchover (automatic or manual), the HAC HMI (hacw_hmi), watchdog, recovery (restart a
  process or tool, hacrec, -wdg_off), mirror / synchronization of the standby, journaling and
  key file repair (isfjrn, *.jrn), history merge after an island situation (hachmfcmd), hac.sup,
  CI_PRIM, hacw_standby / hacw_stop scripts, HAC status items (SYSTEM.HAC1), hacitmval, HAC
  firewall ports (UDP 16000-16006), hardware watchdog or custom health checks, or applying a
  patch to a redundant system. Source IM 36K10J20-01EN.
---

# High availability — HAC (R1.03)

Background: `knowledge/manuals/IM36K10J20-01EN.md` (concepts, processes, set-up steps,
installed `hac.sup` and the differences from the manual).

Rules:
- Run `system-check` first; follow the user's chosen way of working.
- HAC needs its own licence and at least two servers with two separate networks between them.
  Nothing here was practiced on a real redundant pair: say so when giving procedures.
- `hac.sup`, the `tls\com` scripts and system variables need admin rights and a restart; hand
  them to the user (skill `portal-setup`, `change-setup-file.md`).
- Never switch over, reboot or change a server's mode on a running plant without the user's
  explicit approval, and only when the mirror is consistent (see `redundant-setup.md` §3).
- Do not start `hacrec` with `-wdg_off` on a server without reviewing its process list first:
  stand-alone Recovery acts (default action for most processes is `TOOL` = restart services).

| Task | File | Status |
|---|---|---|
| Check HAC on a system: licence, processes, `hac.sup`, scripts, HMI properties, logs | `tasks/hac-checks.md` | verified (read-only, single server) |
| Set up and operate a redundant server pair: steps, `hac.sup` tabs, manual switchover, patching | `tasks/redundant-setup.md` | from docs |
| Recovery, logger and journaling on a stand-alone node | `tasks/standalone-recovery.md` | from docs |
| Dual-redundant Platform for Computer | — | not covered (separate product) |