ci-server-engineer/knowledge/manuals/IM36K10L36-01EN.md

manual	title	edition	version	status
IM 36K10L36-01EN	ITEM Service Engineering - ITM	3rd Edition, Sep. 2023	R1.03	from docs; itm.sup, item_start.cmd and itmdbg statistics checked on the test system (2026-09-30); itmval -g/-p verified in phase 1; itmval -f crashes (ISS-022)

ITEM Service Engineering - ITM (R1.03)

ITM is the real-time item database (item common, shared memory). Section numbers refer to the manual.

1. Processes (§1.1–1.2)

Process	Role
ITM	item handler, message interface
ITMTIM	sends buffered item events; recalculates integrators
ITMCPM / ITMCPS	item copy master / slave for distributed items between nodes (buffered, compressed; after a lost MDUR link it rescans all or only changed master items in limited batches). Restart ITMCPM after deleting a distributed group.
ITMLIMUPD	copies limit/deadband changes to other nodes
ITMREM	cleans up event requests of processes that disappeared
itmval	command-line get/put

itmtim [<period ms, default 100>] [<integration step ms, default 1000>] [<save count>]: save count = integrators saved to disk per recalculation. Installed item_start.cmd starts itmtim 100 1000 1 200 1 (five arguments; the last two are not documented). Also started: itmaah, intitmini, itmlimupd, itmrem.

2. itm.sup (§1.3)

Setting (keyword)	Manual default	Test system
Queue size (queue_size)	200 KB	200
Save items (item_save): ITEM_BASE (per item's remember last value), ALWAYS, NEVER	ITEM_BASE	ITEM_BASE
Max item groups (max_groups)	255	255
Max items per group (max_number)	65534 (255 × 65534 = 16,711,170 items)	65534
Max application info per item (max_appl_info)	≤ 20 bytes always fits	0
Max update info per item (max_upd_info)	512	512
Item pool size (pool_kbytes), guide 0.07 × groups × items + appl KB × groups × items + 10	50000 KB	650000
Integration granule (itm_int_secs), system-wide integrator time unit	1 s	1 (60 tested, ISS-010)
Lock timeout (lock_timeout_secs)	60 s	60
Save to disk (disk_save)	YES	yes
Not regained (not_regained): after start, mark possibly stale values until the first update; hidden in trends	not described	no (default block)

3. itmval (§1.4)

itmval -g [-l] -n <item>
itmval -p [-l] -n <item> [-v <value>] [-s <status>] [-q <quality>] [-o] [-t [<date>] <time> [GMT|LST]]
itmval -f <file> <vsqo> [-l] -n <item>

-l = use this node instead of the host; -o = overwrite a blocked item; -t = update time (default local time). -f should append an itmval -p … restore line with the chosen parts (value, status, quality, options) to a command file, but on the test system it crashes (segmentation fault / access violation) and writes nothing (ISS-022). The manual's space-separated name form (-n <inst> <unit> <tag>) is rejected ("no (extra) command line arguments allowed"); use the dotted full name. Practiced: skill system-management, task read-write-item.md.

4. itmdbg (§2)

Start itmdbg, then a code; answers can be piped, e.g. read-only statistics: printf '2\n-1\n' | itmdbg.

Code	Shows / does
1	main info (root pointers, criterion and event request bits)
2	statistics: common size/free/fragments, configured limits, nr of items, integration secs, save mode, counters (item/sub-item updates, gets, buffered events, automatic saves, flow control) since system start and since debugger start
3 / 4	item / sub-item info by group and sequence number (value, status, options, limits, update times, name)
5–11	action blocks, main actions, task table (event requesters), event buffers, mask info (criterion bits: 1 FIRST, 2 EACH, 4 VAL, 8 STA, 10 DEL, …), item pointers, last update
12	unlock item data area (after a killed process; if pointers were being changed, restart ITEM Service)
13	save all item info to disk (before a shutdown, for a clean warm restart)
14, 15, 17, 18	flow control, integrator list, locked items, group–node relation
16	delete item from the in-core database (test/repair only)
19 / 20	most frequently updated items (10–1000) / reset those counters

Test system (itmdbg code 2): common 665,600,000 bytes, free 665,307,508, 203 items, integration 1 s, save mode item base. The same numbers appear in the automatic snapshots smd_*_itmdbg_all.log (skill system-management, task tuning-checks.md).