Question & Answer
Question
What is the behavior of the ClearCase Local Client (CCLC--the client that supports dynamic and snapshot views) ) over networks that are non-LAN (Local Area Network) based, such as Wide Area networks (WAN), Metropolitan Area Network (MAN), Remote Access Service (RAS), Virtual Private Network (VPN) or others?
Answer
The ClearCase Local Client (CCLC) is designed to operate on a LAN (typically a network with low latency, or small packet Round Trip Times (RTTs)). Users of the local client over connections such as Microsoft Remote Access Server (RAS), Virtual Private Network (VPN), Wide Area Network (WAN) or Metropolitan Area Network (MAN) will experience performance degradation or product failure.
Note: The performance metrics described in this technote also apply to license servers, including FLEXlm.
ABOUT CLEARCASE LOCAL CLIENT PROCESSES
Processes running on ClearCase Local Client (CCLC) machines send many Remote Procedure Calls to processes on ClearCase server machines. These RPCs (and their responses) are small, typically 60 - 100 bytes. A ClearCase command, such as a simple checkout operation, will typically generate 1-300 RPCs.
Reasonable ClearCase performance is attained on networks where the round-trip time (RTT) between ClearCase Local Clients and ClearCase server machines is small - of the order of 1 or 2 milliseconds. While the product continues to function as RTTs increase towards 10 ms and 20 ms, performance is increasingly degraded in these environments. In networks with RTTs of 100 ms or MORE, access to the ClearCase databases can be significantly impacted by VOB locks, whose duration increases as the work that is accomplished while holding the lock is delayed by the longer RTTs.
The use of CCLC over a Wide Area Network, one with RTTs of 100 ms or more is not supported. Severe performance degradations, and frequent long VOB locks will be experienced.
The use of CCLC on networks (such as MANs) with RTTs of 10 ms or less provides degraded but acceptable performance. For example, a checkout command that takes 400 ms in a LAN environment will take 1400-2000 ms on a network with a 5-10 ms round-trip time.
As RTTs approach 20 milliseconds, responses to common ClearCase commands tend to take more than 2 seconds, and this is generally considered unacceptable from a human factors perspective.
The same performance issues also apply when using integrations between CCLC and ClearQuest, where a ClearCase server is accessing a ClearQuest server over a WAN.
WAN-FRIENDLY CLEARCASE
ClearCase Remote Client (CCRC)
The ClearCase Remote Client is designed to operate in non-LAN network environments. The view types that it supports--the Automatic view and the Web view--are analogous to the CCLC view types: the dynamic and snapshot views, respectively. CCRC offers both GUI and CLI user interfaces: ClearTeam Explorer and rcleartool.
ClearCase MultiSite
IBM Rational ClearCase MultiSite extends control of software development assets across geographically distributed environments. In this context, geographically distributed refers to any configuration that is not LAN based.
CLEARCASE USER DOCUMENTATION
For detailed information about installing and using ClearCase, visit the knowledge center:
http://www-01.ibm.com/support/knowledgecenter/SSSH27/welcome
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Document Information
Modified date:
29 September 2018
UID
swg21208931