Sam When I read the original poster's question, I thought he was discribing his environment like this:
CPU1: ICF1, DB2A \__ DB2A and DB2B in the same Data Sharing Group CPU2: ICF2, DB2B / If my simple diagram is correct, then given this configuration, the only way to failure-isolate SCA and LOCK is to system-manage duplex them. I think their options might be described as follows: 1) Accept the cost of system-managed duplexing for his DB2 environment, or 2) If the overhead of system-managed duplexing for SCA and LOCK is too high, accept the outage potential because the structures are not failure-isolated, or 3) Purchase some (cheap? used?) hardware to run SCA and LOCK outside of the hardware footprints where his ICFs and DB2s are running today. Brian On Tue, 11 Dec 2007 11:35:24 -0500, Knutson, Sam wrote: >NO! You don't want to duplex the LOCK and SCA structures. > >We don't do it. >IBM explicitly recommends not to do it under Planning for availability. > >Configure a simplexed SCA and lock structure in failure-isolated >coupling facilities. (When duplexed, the SCA and lock structure do not >need to be in failure-isolated coupling facilities.) >Duplexing the SCA and lock structure offers marginally faster recovery >times compared to dynamically rebuilding a simplexed SCA and lock >structure. Duplexing also enables you to use internal coupling >facilities (ICFs), which provide cost savings over stand-alone coupling >facilities without compromising availability. However, before you decide >to duplex the SCA and lock structure, you should consider that: > >Duplexing the SCA and lock structure does not add significant >availability, because the structures can be rebuilt very quickly from >in-memory data. >Duplexing the SCA and lock structure can cause a significant impact on >performance. In most cases, the overhead that is incurred by duplexing >these structures outweighs the availability benefits of duplexing. > > >The IGS Performance team related that they have found other customers >doing this and the overhead was very high. > > Best Regards, > > Sam Knutson, GEICO > >-----Original Message----- >From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On >Behalf Of Pawel Leszczynski >Sent: Tuesday, December 11, 2007 11:21 AM >To: [email protected] >Subject: db2 lock structures duplexing > >Hello everybody, >I've got a question to guys running DB2 in parallel sysplex environment. >Do you duplex DB2 lock structures i.e. _LOCK and _SCA structure? >What is the overhead connected with it? >In our 2-node PS environment we don't have stand-alnone CF, only >internal CF in two different footprints. >We want to avoid situation when damage of one of the boxes >will bring the whole DB2 sharing group down. > >Regards, >Pawel Leszczynski ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
