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Browse Prior Art Database

Management of Peer-to-Peer Control Unit Paths

IP.com Disclosure Number: IPCOM000116373D
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 102K

Publishing Venue

IBM

Related People

Hathorn, RG: AUTHOR [+2]

Abstract

A method for managing Peer-to-Peer Remote Copy (PPRC) path "status transitions" and a method for updating or modifying active paths between control units is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Management of Peer-to-Peer Control Unit Paths

      A method for managing Peer-to-Peer Remote Copy (PPRC) path
"status transitions" and a method for updating or modifying active
paths between control units is disclosed.

      In a complex configuration of peer to peer remote control
units, the Primary Control Unit (PCU) can also provide a role of
Secondary Control Unit (SCU) and vice-versa under architecture rules.
Fig. 1 is an example of Control Units (CU) configured for PPRC.
Control Units 1, 2 and 3 are configured as both PCU and SCU.  CU 3 is
secondary to CU 1 and 2.  CU 4 is only PCU.  CU 5 is only secondary
to CU 4.  Customer requirements may further complicate the
configuration.   As a result of updating the PPRC configuration, PPRC
path "status transitions" occur and the PPRC "path table" gets
updated.  How this is managed is described in following sections.

      Fig. 2 is demonstration of an OOA model of a PPRC manager.  It
is an information model representing relationship between various
objects.  ESCON attachment object accesses peer to peer CU
information via the Remote_CU_Manager object.  There are two major
pieces of peer to peer CU information.  The first piece identifies
the remote_CU_table and second piece identifies the SCU path
information.  PCU uses this information to perform peer to peer
functions to desired SCUs.

      Fig. 3 describes legal PPRC path status transitions.  Rules for
status transitions are as follows.
  o  Every PPRC path that needs to be established begins with zero
      status or no_status.
  o  From zero status, you can transition to anything but removed
      state.  Note that only an established path can be removed.
  o  You must go through zero status to establish a path.  No attempt
      should be made to establish a path that is already in
established
      state.  This is why transition from established state to
      zero_status is not allowed.  Only allowable transition is from
      established state to removed state.
  o  If a PPRC path can not be established in predetermined time
      period then status is updated to tim...