The recent introduction of SAP’s Always-On HADR solution, (licensed) feature of Adaptive Server Enterprise, will have former Sybase clients thinking, “why did we ever toss Sybase in favor of brand X?” After all, Wall Street was built upon the speed and reliability of Sybase software. No other product came close to its dataserver, replication server, and client/server ground-breaking technology.
ASE and Replication Servers still play an integral part in our data services, especially with regard to speed, data integrity, and heterogeneous capability. I’ve been working with these two products for over 20 years from Replication Server 11.0.2 (when I used to pull my hair out) to the most recent 15.7.1 SP305. Now, in the post-Sybase era, the ASE/RS tag team has been given a fresh tank of oxygen and continues to thrive in the marketplace.
Through the introduction of practical, user-desired features incorporated by SAP, Always-On HADR continues to be a cost-effective, reliable, robust solution for many clients planning or upgrading an OLTP, HA, or DR environment.SAP ASE Always-On HADR option Dobler Consulting has performed extensive evaluation and testing on the SAP Always-On HADR feature.
Dobler Consulting has performed extensive evaluation and testing on the SAP Always-On HADR feature. We have written a detailed technical paper with our findings so that you can gain a better understanding of the feature and how it works.
In the paper, you’ll learn about all the various testing we carried out and the results they yielded. Our team of experts has worked diligently to put together all of the technical details needed to enable you to implement the HADR feature.
We want you to know what’s in our paper before you download it. Here is a high-level summary of what it contains. You can download the SAP ASE Always-On White Paper.
Please note: The information contained in the technical document pertains only to the High Availability configuration, operation, and administration of SAP’s Always-On HADR feature.
Think of the Always-On feature as a high-availability and disaster recovery (HADR) solution that, currently, consists of two SAP ASE servers, two SAP Replication Servers (RS), two SAP Host Agents, and a Fault Manager (FM) to monitor and control component failure switching.
The answer is, YES. I recently downloaded, installed, and conducted a series of comprehensive tests to help me understand Always-On. You may think, “synchronous replication; no way, my users will be sitting around waiting for the keyboard to unlock!.” However, you may be surprised. Through the use of a robust network combined with fast disk devices synchronous replication works well and it guarantees zero data loss (ZDL).
In a properly configured HA environment, users will not experience a degradation of throughput.
The tested Always-On bundle consisted of the following products:
|SAP Adaptive Server Enterprise (ASE)||(re-energized and still lightening fast)|
|SAP Replication Server (RS)||(new commands/functionality, enhanced automation)|
|SAP Host Agent||(os/database monitoring, instance provisioning)|
|Replication Management Agent (RMA)||(…more than your father’s Replication Server Manager)|
|SAP ASE Cockpit||(…more than your father’s Sybase Central) (not discussed in this document)|
|Fault Manager (FM)||(…more than your father’s OpenSwitch)|
The basis for the design is a cluster configuration. The cluster we configured for our testing consisted of two sites:
The process flow was from the primary ASE (site1) to the primary RS (site2) then into the companion ASE (site2). We did not use the RS (site1) in this scenario. Upon automatic or manual failover, replication changed direction to flow from the new primary ASE (site2) to the new primary RS (site1), then into the new ASE companion (site1). The RS (site2) was not used in this scenario.
Here is a good depiction of the architecture courtesy of SAP’s “HADR Users Guide – Administration Guide – SAP ASE 16.0 SP02 – December 20, 2016”
The normal path is in green and the failover flow in dotted red.
The installation is a straight forward 3-step process.
Based on initial testing, it seems as though SAP put some manpower behing the QA of this product. The performance was a nice added bonus because it eliminated our team from having to do a lot of QA on our end, like we’ve experienced in the past.
For the most part, I can say that everything worked as advertised and most of the problems encountered were caused by being unfamiliar with new command syntax and the use of these commands. Failover, manual and automatic, was swift and clean.
For my minimal testing environment, component failover completed in 5-7 seconds. The FM, working in conjunction with the Host Agent and RMA, successfully detected primary ASE failures and performed failover/failback as it should. I am hoping, however, that a future release of the FM, which is basically a reworked OpenSwitch (HA product marketed by Sybase in the past), supports some sort of a “Coordination Module” interface to allow clients to introduce their own criteria and tasks to be performed during pre and post failover.
The AO software version described in this document was ASE 16.0 SP02 PL05 HF1. The RS software within this bundle was at 15.7.1 SP305.
Selected content for this document has been obtained from the “HADR Users Guide – Administration Guide – SAP ASE 16.0 SP02 - December 20, 2016”.
ALWAYS-ON. The product is aptly named and will not disappoint.
ALWAYS-ON is not your father’s SAP Replication Server HADR solution!