Lozen, Record Level Sharing (RLS), and Transactional VSAM (TVS)

In a prior blog, we discussed how we designed Lozen™ to leverage the robust data integrity options provided by VSAM on the mainframe.  With Lozen, you have the identical levels of access and integrity you would have if your application were running natively on z/OS.  This includes support for Record Level Sharing (RLS) and Transactional VSAM (TVS), which we cover in more detail here.

VSAM RLS provides concurrent read-write access, but it does not include transactional recovery (commit/rollback) like CICS.  Because of this, customers sharing VSAM RLS files with CICS systems will tend to limit non-CICS applications to read-only access.  In most configurations, when updates need to occur, the files would either be marked “read only” to CICS or put offline to CICS.  Lozen operates under these same rules.

If a higher degree of integrity is required, the typical solution would be to leverage “Transactional VSAM” (TVS), which provides full transactional logging and capabilities that make it practical to have read-write sharing with CICS systems within a sysplex.

The caveat is that applications not designed around any type of transaction processing may need to be reviewed to ensure they are not inadvertently retaining record locks.  TVS normally locks records from the time they are accessed until either the file is closed or until the application issues a COMMIT (or rollback).  Applications updating many records may thus retain record locks for a lengthy amount of time until the file is closed.

To help with this, Lozen has an optional capability that can automatically commit record updates on VSAM TVS files, if desired. When this option is set, Lozen automatically commits record updates (thus releasing any retained record locks) after every “n” updates, where “n” is a customer-selected record count that can be any arbitrary number from 1 (that is, commit after every update) to some larger number.

Applications can also be upgraded to include a more intelligent transaction management approach, but such an approach would require application changes.


Lozen is VirtualZ Computing’s revolutionary solution that unlocks the power of real-time, read-write data access — from any platform, anytime, anywhere.

By design, Lozen leverages the robust data integrity options provided by VSAM on the mainframe, including support for RLS and TVS.

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To learn more about how to unlock the power of real-time, read-write IBM zSystems data access with Lozen:

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