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STP Save configuration across Power Outages for two server STP-only CTN

July 13, 2009Gregory Hutchison - May 10, 2012 updateGregory Hutchison - January 23, 2013 update

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Agenda

Prerequisites and set up required

Enablement of “Save configuration” function

CTN configuration rules after “Save configuration” function enabled

Rules for restoring roles (PTS/CTS, BTS) after the power is restored

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STP configuration and time information saved across power outages – two server CTN

Previously

– If both servers experienced an unplanned power outage, user had to:

• Initialize the Time; • Redefine the PTS, BTS, CTS roles

System Management Enhancement

• STP CTN configuration (PTS/CTS, BTS) can be configured so that – PTS/CTS, BTS roles possibly restored after a power outage– Initialize Time not required

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Prerequisites / required set up

MCLs required:– zEnterprise (zEC12, z114, z196) has this support integrated

– z9 EC and BC Bundle 44

– z10 EC and BC Bundle 26

– Function not available on D55 (z990, z890)

If migrating from ETR network – PTS/CTS and BTS must first be assigned using procedures outlined in Server

Time Protocol Implementation Guide, SG24-7281

If setting up a new STP-only CTN– PTS/CTS and BTS must first be assigned using procedures outlined in Server

Time Protocol Implementation Guide, SG24-7281

STP-only CTN can only have two servers to enable this function– If more than two servers in operational CTN,

• Remove additional servers in the CTN by assigning them to a different to a different CTN, if possible

• Cannot proceed with this enhancement with more than two servers in CTN

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Enable “Save configuration” enhancement

Launch the System (Sysplex) Time task of the server that is the CTS

– Go to the Network Configuration tab

– Check the box “Only allow the server(s) specified above to be in the CTN”

– Click Apply

– “Only allow the server(s) specified above to be in the CTN” can be enabled only if two servers can communicate over coupling links

• Cannot select “Force Configuration” and “Only allow the server(s) specified above to be in the CTN” at the same time – error message generated

Note: Recovery and re-takeover rules unchanged for a CTN with PTS and BTS assigned

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Rules after applying “Only allow the server(s) specified above to be in the CTN”

If any other server besides the defined PTS, BTS attempts to join the CTN, it will not be allowed to join the CTN

You can disable “Only allow the server(s) specified above to be in the CTN” only if 2 servers communicating over coupling links

You must disable (uncheck) “Only allow the server(s) specified above to be in the CTN” before any of the following actions are allowed:

– Any server role assignment changes

• Includes moving CTS role from PTS to BTS when disruptive action planned on PTS/CTS

– A local CTN ID change

– A reverse migration from STP-only CTN to Mixed CTN

If you intend to upgrade one of the servers in the CTN to a new machine type, and have it rejoin the same CTN, you must disable (uncheck) “Only allow the server(s) specified above to be in the CTN” before the upgrade, otherwise the server will not be allowed to join the CTN

– Example of upgrade:

• z196 to zEC12

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Resuming PTS/CTS, BTS roles after outage of both servers

Both servers remain unsynchronized (S0) until they can communicate either over – Coupling link path or

– LAN path (Console Assisted Recovery (CAR))

If servers can communicate over coupling link path, – PTS->S1 and BTS->S2

If servers cannot communicate over link paths, but can communicate over LAN path, CAR initiated– Actions taken by PTS

• If PTS determines BTS is “dead” or S0– PTS -> S1– When link paths restored, BTS will become S2

• If PTS determines BTS is S1– PTS -> S0– When link paths restored, PTS will re-takeover as S1

• If PTS cannot determine state of BTS– PTS -> S0

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Resuming PTS/CTS, BTS roles after outage of both servers (continued)

– Actions taken by BTS

• If BTS determines PTS “dead”– BTS -> S1– When link paths restored, PTS will become S2 first and re-takeover as S1, if

originally assigned CTS• If BTS determines PTS operational

– BTS -> S0 – When link paths restored, BTS will become S2

• If BTS cannot determine state of PTS– BTS -> S0

If servers cannot communicate over link paths and LAN path,

– PTS -> S0

– BTS -> S0