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Ensuring 100% Consistency Between Replicated Databases

Why It’s Challenging, How We Can Help



Within most enterprises running HPE NonStop systems today, production and business continuity environments are very complex. These environments typically include very large, multi-partitioned databases, including both audited and un-audited files. In addition, these environments usually support various access methods, including Enscribe, OSS, SQL/MP, and SQL/MX.

In these NonStop environments, it is common to have replication being performed, for example between load balanced or business continuity environments. In these environments, it is vital to ensure replicated instances are entirely consistent. If they’re not, business services can encounter processing errors, leading to very lengthy and costly recovery times.

However, it can be very challenging to ensure databases are always 100% in sync. In NonStop environments, data validation isn’t being performed. While vendors offer data replication solutions, these tools do not guarantee that files are in sync. In fact, many replication vendors also offer separate data validation solutions that are designed to keep files in sync.

This leaves teams to contend with two fundamental challenges:

The good news is that FS Compare and Repair is a solution that uniquely addresses both of these challenges.

Introduction to FS Compare and Repair

FS Compare and Repair offers fast, advanced capabilities for ensuring your nodes are kept in sync at all times. The solution employs a market-leading, block-level approach that offers breakthrough speed and scalability and supports some of the most complex environments.

For example, customers use the solution to validate their data in four-way production environment configurations. In these scenarios, customers have four copies of data. For illustration purposes, we’ll refer to these as systems A, B, C, and D. Teams use an online replicator to send any updates made on one system to the other three systems. If updates are made to system A, the online replicator will send these updates to systems B, C, and D. Meanwhile, FS Compare and Repair can be used to validate and, if needed, repair the data between the four systems.

Enhanced SYSKEY Support Delivered

FS Compare and Repair also offers capabilities for preserving SYSKEY values in SQL/MP and SQL/MX databases.

For those unfamiliar with this aspect, SYSKEY is a unique, system-generated value that is used when no primary key is defined. For tables that don’t have key columns defined, a column for SYSKEY will be generated (which is referenced as “SYSKEY CHAR(8) BYTE”). This column contains the SYSKEY generated by the specific system hosting the table. By default, the system generates this value when inserting a value into a table.

Given this, tables in each copy of a database residing on different systems would be different. Consequently, in replicated environments, a source row would differ from a target row.

FS Compare and Repair can exclude these SYSKEY values when doing comparisons. When doing repairs, the solution can preserve the SYSKEY values unique to each database instance. FS Compare and Repair now supports two methods to preserve the SYSKEY values in SQL/MP and SQL/MX during an insert operation:

  1. Block repair mode. The solution has featured this functionality for some time. In this mode, the solution will acquire exclusive access and then update a target table. Consequently, other applications will not have access to the table during the update.
  2. Record repair mode and repair override SYSKEY option. Now, with its new SYSKEY override capabilities, FS Compare and Repair can make updates without the exclusive access requirement of block repair mode. As a result, a target table will be updated with no interruptions, while enabling other applications to access the same table. This enhancement provides a transparent method to repair SQL/MP and SQL/MX tables that feature SYSKEY values, while preserving the target table’s SYSKEY values.

Validation and Repair of Enscribe Alternate Key Files

If discrepancies exist between Enscribe Primary Key or Alternate Key Files, business services may be affected. These discrepancies can lead to lengthy outages and time-consuming recovery efforts. FS Compare and Repair can ensure that these Key files are kept in sync.

Additional New Capabilities of FS Compare and Repair

In addition to enhanced SYSKEY support, FS Compare and Repair has also received additional new capabilities:


In addition to our FS Compare and Repair solution, TANDsoft offers a range of solutions for teams running critical workloads in NonStop environments. To learn more, be sure to visit our web site, In addition, you can visit the TANDsoft team at the following events: