Mixed-mode operation for VSAM data sets

Generally, you choose which data sets need to be shared and updated in RLS mode by multiple CICS regions. When you have made this choice, you are recommended always to update these data sets in RLS mode.

However, with RLS support, data sets can be shared in mixed access mode, between CICS regions and batch jobs. Mixed access mode means that a data set is open in RLS mode and a non-RLS mode concurrently by different users.

Although data sets can be open in different modes at different times, all the data sets within a VSAM sphere normally should be opened in the same mode. (A sphere is the collection of all the components—the base, index, any alternate indexes and alternate index paths—associated with a given VSAM base data set.) However, VSAM does permit mixed-mode operations on a sphere by different applications, subject to some CICS restrictions. In the following discussion about mixed-mode operation, references to a data set refer to any component of the sphere.