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z/OS Encryption Requires ICSF to Start Early in IPL

Document Author:

Kathy Walsh

Document ID:


Doc. Organization:

Advanced Technical Sales

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Product(s) covered:


Abstract: Users of encryption need to ensure ICSF is available across the widest IPL window possible.

Customers planning on using the z/OS data set encryption function need to ensure that ICSF is started early in the IPL process. This is especially true if customers plan to encrypt SMF data sets or other data sets used during z/OS initialization. As such, it is highly recommended a command be placed early in the COMMNDxx member to ensure there is minimum delay in z/OS initialization.:

S CSF,SUB=MSTR (or appropriate PROC name)

Specifying SUB=MSTR is necessary to allow ICSF to start before JES. Furthermore, during z/OS system shutdown, ICSF should be one of the last features to be terminated so dependent functions are not impacted. It is highly recommended ICSF be brought down after terminating the JES address space and after initiating SMF halt processing. Note that since ICSF is brought down after SMF is halted, there may not be an SMF record cut for the termination of ICSF.
For additional details, please see the ICSF System Programming Guide:

IBM Knowledge Center:






S/W Pillar(s):

IBM System z Software




ICSF, encryption, IPL, DFSMS, z/OS

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