Browse Prior Art Database

TWO WAY HAND-SHAKING VOB SYNCHRONIZATION A New Approach To Clearcase Multisite Re-Synchronization

IP.com Disclosure Number: IPCOM000009051D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Aug-05
Document File: 7 page(s) / 457K

Publishing Venue

Motorola

Related People

Howard Zhou: AUTHOR

Abstract

ClearCase, developed by Rational Software, is a premier Software Configuration Management tool that allows users to store any information under ver- sion control in a centralized repository. This cen- tralized repository is also called a VOB (Versioned Object Base). MultiSite feature of ClearCase allows users from different sites to share the information in a VOB. In order to do that, the VOB needs to be replicated and a replica of the VOB will be shipped to each site. The VOB replicas at all sites need to be synchronized.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 13% of the total text.

Page 1 of 7

0 M

MO7VROLA Technical Developments

TWO WAY HAND-SHAKING VOB SYNCHRQNIZATION A New Approach To Clearcase Multisite Re-Sjmchronization

by Howard Zhou

INTRODUCTION

  ClearCase, developed by Rational Software, is a premier Software Configuration Management tool that allows users to store any information under ver- sion control in a centralized repository. This cen- tralized repository is also called a VOB (Versioned Object Base). MultiSite feature of ClearCase allows users from different sites to share the information in a VOB. In order to do that, the VOB needs to be replicated and a replica of the VOB will be shipped to each site. The VOB replicas at all sites need to be synchronized.

  The VOB replicas are synchronized via some data packets that are transmitted through TCP/IP network among these sites. The sync packets are applied to the VOB replicas sequentially. If one sync packet was missing during the transmission, any subsequent packets can't be applied to the cor- responding VOB replica.

  If incoming packets cannot be applied to the VOB replica, the VOB is out of sync. Users of this VOB replica will not be able to see any updates from the other site. The out sync problem can become critical in timely manner w.hen two sites work closely to each other. In the worst scenario, the VOB replica has to be abandoned and a new

replication will be requested.

OUT OF SYNC PROBLEM

  ClearCase MultiSite software does not detect if a VOB replica is out of sync and does not provide a way to re-synchronize automatically either. Therefore the out of sync problem has to be dealt with by human intervention. A ClearCase adminis- trator at one site cannot handle the problem alone. He must contact his/her counterpart at the other site

to obtain information on'the sync status. Based on the information, he/she can reset the VOB and re- ship the missing packets, to the other sites. Having received the sync packets, his/her counterpart would try to import these packets to the VOB and verify the sync status again.

  This manual re-synchronization process is tedious work and sometimes could take a long time to accomplish. One time, we had 8 VOBs out of sync at the same time. Due to the constant changes in each VOB on a daily :basis, it took three months to get all the VOBs back: m sync. If the out of sync problem was not resolved in a timely manner, changes to the VOB would be accumulated and the gap between two sites would get bigger. The size of sync packets would be getting so big that it will not work to use the automatic store-and-forward ship- ping mechanism provided by the vendor. Instead, a manual ftp has to be arranged to transfer these huge size packets.

  The root cause of this sync problem is that there is lack of two-way handshaking acknowledgment during the sync process. In other words, the sending site does not know if the'receiving site has received the packets. Without any confirmation, the sending site keeps sending new packets to the receiving s...