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Welcome to the System z Coupling Facility Structure Sizer Tool (CFSizer). CFSizer is a web-based application that will return structure sizes based on the latest CFLEVEL for the IBM products that exploit the coupling facility.

Any use of the CFSizer Coupling Facility Sizer Tool indicates that you have read the disclaimer and accept the terms.

CFSIZER is useful when you introduce a new workload or application, change an existing workload in some way, or wish to revalidate your current structure sizes. For each structure, it accepts inputs that characterize the structure workload in terms meaningful to the associated application. It then uses your input to calculate the number of structure objects the structure must contain, based on algorithms provided by the structure owners that model their use of the structure. Using these results and structure attribute information provided by the structure owners, CFSizer then submits a calculation request to an IBM-owned coupling facility, using the IXLCSP programming interface. The coupling facility itself calculates the structure size required to accommodate the specified input. Structure sizes therefore correspond to the CFLEVEL installed on the coupling facility that performs the calculations, which will normally be the highest level currently available. The CFLEVEL for which the recommendations were calculated is displayed on the output page and is not selectable. Structure sizes are displayed with units of K, M, G, or T, and can be entered in your CFRM policy as displayed.

The inputs you supply should correspond to your expected peak usage of the product. It is generally good practice to slightly overspecify your peak values, to produce a sizing recommendation slightly larger than absolutely necessary. This will provide some room for growth, and help avoid failures caused by insufficient structure sizes.

To size a structure, click on one of the product links in the drop-down menu (e.g. XCF, Db2, JES, etc.) to access that product page. From that product page, select one or more structures to size by clicking the product's checkbox. At least one structure must be checked to submit a request for a structure size.

We have purposely simplified the interface to request as few inputs as possible. However, in some cases, it still might not be obvious what input data is being requested. For product help, click on the help link provided on each product page. A help window will open that will provide some additional detail about the product and the input fields.

If you are upgrading your CFCC microcode on one or more CFs, you are confident that your existing structures are adequately sized, and you simply want to know how much they may need to grow to accommodate the same workload at the new CFCC level, you may be able to use the current structure sizes to calculate the new sizes.  Click here to evaluate alternate sizing techniques. However, IBM recommends that you periodically recalculate your structure sizes through CFSizer, based on expected usage and structure attributes.

Please send any comments, suggestions or problems related to the CFSizer tool to

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Document Information

Modified date:
03 September 2021