OS Integration: Directory Structure & Users

A colleague proposes 'prd' as the SID for the new production system. It's short and three characters, yet installation rejects it. What are the hard rules for a valid SID?

At install you're prompted for both a SAPSID and a DBSID. Can they differ, should they, and is there a case that forces them apart?

OS-level abbreviations like ms, dw, and gwrd tell you a process type but not what an SAP process is currently doing. Where are those abbreviations defined, and what are ms and gwrd?

You already watch the fill level of the database and log filesystems. Why does SAP insist you also clean up the transport and instance directories, and what actually breaks if you don't?

Under the \usr\sap root you see two Windows shares, sapmnt and saploc, but on a UNIX host you don't. How is the same central-access mechanism achieved on each OS?

The team wants 'SAP' or 'TMP' as a memorable system ID. Both are three capital letters starting with a letter, yet the installer still blocks them. Why?

On a UNIX SAP host running MaxDB, which second OS user besides <sid>adm is created, and how is its name formed?

You create a second database user to let a reporting tool read SAP tables directly at the DB layer. It sees nothing. Who actually owns the SAP tables?

In a UNIX ps -ef listing, saposcol shows up once, owned by root with PPID 1 — not under <sid>adm or sapstart like the other SAP processes. What is it and why does it sit outside the instance tree?

At the OS level you see two sibling processes co.sap<SID>_<instance> and se.sap<SID>_<instance>. They look like a pair — what distinct roles do they play?

Every work process of an instance shows the identical OS abbreviation dw, so they all look the same in ps. How do you single out the dispatcher among them?

A work process crashed on one instance. Among the per-instance log, work, and data directories, which do you open first for the trace/error detail, and why not the others?

You need to find where a transaction sits in the menu tree. A colleague says 'just open SE16 on TSTCT.' Will that give you the menu path, and if not, what does?

You edit a profile parameter under /usr/sap/<SID>/SYS on a distributed system with app servers on several hosts, expecting it to affect only the local instance. Is that assumption right?

When provisioning OS users for an SAP system, what's the key difference between UNIX and Windows in how background/service tasks run, and which account is easy to forget on Windows?

SAP support asks you to run a debuggable kernel to analyze a crash. Inside the exe directory (dbg, opt, run), what exactly do you switch, and what's the cost of leaving it switched?

On a distributed SAP system, why must /sapmnt/<SID> be a single shared filesystem rather than a separate copy on each host, and what breaks if a host can't reach it?