Changing IBMi host name search priority - best practice

valmatic used Ask the Experts™
Hi.  We haven't changed our network structure on the IBM I for years and only recently have a need to as all of our processes have been pretty much contained on the I.  I'm self taught in IBM maintenance and learning as I go but I think the changes I need to make are pretty benign but I need some advice.    

I noticed my host table is totally out of whack with my network so I need to remove and correct some entries.  I'm really thinking about only leaving those entries referencing my Virtual IP on the I and otherwise not using a host table.  Ultimately, I need to add some DNS entries and allow external resolution.  Currently my Host name search priority field under CHGTCPDMN is set to *LOCAL.  Is it necessary to change to *REMOTE to make DNS active?  Would this change require an IPL?   If I leave that setting at *LOCAL, Do I need to make a specific entry in my host table or will lookups query my host table and then automatically jump over to DNS for those  queries without a corresponding entry, provided I have the DNS server addresses listed?  
I guess my question(s) are, What is best practice in this case?   Do Host table changes or DNS changes require any service restarts or an IPL or can I just make these changes on the fly?
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For consistency with other systems, HOSTSCHPTY(*LOCAL) is probably the most consistent.  Most operating systems search the local host table first, and DNS if a local hit isn't found.  This setup will confuse network administrators the least.

Local searches are also the fastest.  This allows you to set up commonly used hosts in the local host table, and improve performance of critical lookups.  OF course, this comes with losing the flexibility of central control in DNS.

HOSTSCHPTY(*LOCAL) tells the system to search the local host table first, and if the host isn't found, search DNS.
HOSTSCHPTY(*REMOTE) tells the system to search DNS for a host name first, and only do a local search if the host is not found in DNS.  

I suggest you do one of the following:

Only use DNS.  If that is the case, the local host table will be empty, and you can do *REMOTE to skip the local lookup step for most host lookups.

Use DNS for most hosts, but use the local host table for critical hosts you can't afford to lose access to if DNS goes down.  Either setup gets you protection here.

Host table changes and DNS config changes take place immediately.

IBM offers comprehensive documentation of IBM i DNS planning, configuration, and administration.  Do yourself a favor and read the instructions :-).


Hi Gary, Thanks for the great info.  I did read through the documentation through that link and it helped narrow the focus of what I really need to do but I think I just needed real speak vs. IBM speak..  So thanks for that.  In the Windows networking world, I make these changes without over-thinking it but, even though IBM is just another server OS, it has a lot of special needs and I find myself doubting or over-thinking my actions.  Anyway, thanks as usual..  Your insight is always welcome.

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