198 IMS in the Parallel Sysplex, Volume I: Reviewing the IMSplex Technology
Logon rejected
Then, in Figure 8-15, if the user gets tired of waiting (maybe the user knows that IMS1 will be
down for an extended period of time) and logs on directly to IMS2, IMS2 will check the NodeA
entry and find that NodeA is owned by IMS1 and reject the logon.
Too bad;
however, IMS2 can steal the node if the logon exit (DFSLGNX0) says it is OK. A
clever user shop will write a logon exit to recognize some user data entered at logon as a
request to steal the node. For example, the user data might say,
I really mean it!. If this
happens, then the conversation is not recoverable. When IMS1 is restarted and finds the
resource with recoverable status and SRM=LOCAL, IMS1 will check the resource structure
and discover that NodeA/UserA/etc. are no longer owned by IMS1 and delete the status. That
conversation is gone.
Figure 8-15 Status recovery (SRM=LOCAL)
8.8.3 Status recovery (SRM=NONE)
SRM=NONE (or RCVYxxxx=NO) means that end-user status is not to be recovered, even
locally. When a session terminates with SRM=NONE, all end-user status is deleted. See
Figure 8-16.
This might be useful with ETO, which will not delete control blocks if there is any status. For
example, an ETO STSN device ALWAYS has status (always has a sequence number).
SRM=NONE for these devices would delete the status, and then the resources themselves
could be deleted.
VTAM (Generic Resources)
CF
S
C
I
CQS
OM
SCI
IMS
CTL
S
C
I
RM
SCI
SCI
SCI
SCI
IMS2
S
C
I
CQS
OM
SCI
IMS
CTL
S
C
I
RM
SCI
SCI
SCI
SCI
IMS1
LOGON IMS2
NODEA
LTERMA
NODEA
LTERMA
VGR affinity
set to IMS1
SRM=LOCAL
Recoverable
Message
Recoverable Status
Owner=IMS1
SRM=LOCAL

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