Lizette, the best description for the rebuild process can be found in the sysplex services guide, chapter 5.5 (z/OS 1.8). It is a multiple phase process that was added to over the years. Rebuilding a structure generally means that the location of the structure is changed. Altering a structure means that the structure stays in place and some *internal* changes take place (like a change in the entry-to-element-ratio or in the size).
The preference list is what XES uses to initially allocate a structure. The order in the preference list describes the installations' preferences for the location of the structure. XES also takes some attributes into account that the first connector to the structure had specified, so it may be that a structure ends up somewhere else than the first CF in the preference list. When you duplex a structure, it stays in a permanent rebuild state (the last phase of the rebuild - fallover to the new structure is not done, and despite that all connectors can again issue requests to the structure. This is not the case when a structure is in 'simple' rebuild). Obviously, you want to duplex into another CF as a precaution against losing the first cf. In that case the system would automatically 'complete' the rebuild process by falling over to the other side, thus eliminating most of the time that is needed to start and complete a system-initiated rebuild due to loss of connectivity. So generally, the 'original' structure is in the first CF in the preference list, and the duplexed structure is in the second CF in the preference list. The difference between a rebuild/duplex done via connector participation or via system-initiated rebuild/duplex is exactly that - the participation needed by every connector. The rebuild protocol is rather complex, with lots of events that need to be responded to by every connector before the next phase can be done. Originally (back in MVS 5.1) there was only connector-managed rebuild. Some structures (like the jes checkpoint) never implemented that protocol. Then came system-managed rebuild, which took connector participation away. A JES2 checkpoint can be rebuild by XES automatically. As far as I remember, when the connector supports the rebuild protocol, then the system requires connector participation. Altering a structure is another beast entirely. When the CFRM policy specifies different values for initsize and size, then this structure is allocated using the initsize value. It can be altered to a bigger size via the setxcf alter command *without* activating a new CFRM policy. When autoalter was invented, the minsize parm was added. My memory is fuzzy how that size comes into play. ALLOWAUTOALTER guides if XES can change the size of the structure without you doing anything about it (I believe it did in your display) and/or the entry-to-element-ratio and maybe some other stuff that escapes me right now. You say "So are you saying that it is better to use DEPLEX(ALLOWED) rather than DUPLEX(ENABLED)? How does that help DB2? And we are considered a small to med DB2 shop because we have less than 5000 TB/DBs." Duplexing in itself *only* helps to keep down the rebuild time in case of a failure of one CF. The structure is then available in the other CF and can be used immediately in the other CF. Duplexing a structure comes with a cost to response time. When a structure is duplexed, XES does two operations to both CFs that have this structure allocated, and XES has to synchronize that changes to one structure are also present in the other. So response times for an operation to that structure are longer when the structure is duplexed. If you're a high availability shop, then that may be what you want. On the other hand, when it is possible that the loss of one CF may impact your system rather seriously (as in IPL and/or loss of any subsystem), then you may not want to duplex in the first place. Having DUPLEX(ENABLED) or DUPLEX(ALLOWED) in the policy also determines if XES attempts to immediately (re-)duplex the structure into a third CF, if there is one. Hope your eyes are not crossing yet after reading this.... Regards, Barbara -- GMX FreeMail: 1 GB Postfach, 5 E-Mail-Adressen, 10 Free SMS. Alle Infos und kostenlose Anmeldung: http://www.gmx.net/de/go/freemail ---------------------------------------------------------------------- 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
