--- title: "17 Top VSAM Tuning Tips" description: "Single point reference to VSAM tuning tips. These are useful for mainframe projects." url: https://srinimf.com/2016/06/08/vsam-tuning-tips-to-use-in-mainframe-projects/ date: 2016-06-08 modified: 2026-10-10 author: "Srini" image: https://i0.wp.com/srinimf.com/wp-content/uploads/2016/06/vsam-tuning-tips1.jpg?fit=1200%2C900&ssl=1 categories: ["VSAM"] tags: ["VSAM best tuning tips"] type: post lang: en --- # 17 Top VSAM Tuning Tips Tuning VSAM files tips are necessary to improve file performance. Data with Index faster in response, so these are useful to apply in the mainframe projects. Related[8 Necessary Skills Data Engineers Should Learn](https://srinimf.com/2014/06/30/skill-set-for-analytics-professional/) Related[You Should Always Know These 15 AWS Services Too](https://srinimf.com/2022/08/06/15-comprehensive-interview-questions-on-aws-additional-services/) ## VISAM Tuning Tips 1. Always use efficient Data and Index CI sizes. 2. Assuming your record size permits, 4K/8K works best for the Data CI size of 3. CICS online files. The Index CI should be large enough to hold all of the index entries for a DATA. VSAM is clearly explained in the [express edition.](http://www.amazon.in/gp/product/9382715827/ref=as_li_tl?ie=UTF8&tag=srinimf-21) 4. For large keys that do not compress well, this could be 8K/16K. Too small an Index CI may result in unnecessary CA splits. 5. The Index CI should be also large enough so that Index Levels is no more than 2 if possible. You can make it too big but 2K is often too small. 6. Always define your [VSAM clusters](https://www.amazon.in/gp/product/0911625453/ref=as_li_tl?ie=UTF8&tag=srinimf-21) with the SPEED parameter. 7. CI and CA Splits can greatly reduce CICS response time. 8. Code CI and CA Freespace very carefully and monitor regularly. 9. REORG of files does NOT fix splitting problems. It just covers the problem up for a short period of time. 10. Allocate better FREESPACE. 11. 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