If you're currently using Oracle Database Standard Edition, or considering using it to reduce your Oracle spend; you probably know that your High Availability and Disaster Recovery options are limited; there's no DataGuard, and, effective with Oracle 19c, RAC, even RAC One Node, is no longer an option. What to do? Oracle suggests either upgrading to Enterprise Edition, or using Oracle's newly announced SE HA capabilities.
HA and DR - An Overview
High Availability and Disaster Recovery are related, but not quite the same thing. For a more complete discussion of the differences, and why most businesses need to plan for both, see my earlier blogs in this series.
Considerations for SEHA
SEHA is an "adequate" HIgh Availability solution, but there are some limitations that need to be considered.
It's only HA, not DR
First and foremost, since SEHA uses Oracle Clusterware and ASM, both the primary and standby (or failover) servers have to be located in the same data center, AND connected to shared storage. While that's a great HA choice, if there's a fire in your data center, or, to paraphrase Dilbert, if your data center gets hit by a meteor, or, much more likely, an earthquake, your business critical application is unavailable.
The database is still a single point of failure
Just as with RAC., SEHA uses a single database, or set of files. Even if you don't lose your entire data center, if your storage is unavailable, so is your application.
The standby is just that, "standing by"
Since SEHA is based on failover technology, the database, and your application, can use only one server at a time. The resources on your standby server can't be used for reporting, or workload isolation, or load balancing. And by the way, the Oracle SEHA license limits you to 10 days of use on the standby. Can you guarantee that you rebuild an entire server in less than that? Since these issues aren't really DR or HA, we'll cover how SharePlex lets you share data between servers in a separate blog.
But, wait, there's more
As I mentioned earlier, SEHA requires Oracle ASM, Oracle Clusters and Oracle Grid Control. You probably have all of those configured somewhere in your environment; but, are they correctly configured for SEHA. How do you know, without actually performing a failover, that the database will come up and run on the standby system? Also, SEHA supports only heterogenous hardware/OS/Database versions. What happens when you want to upgrade?
SharePlex - The Golden Alternative
Fortunately, there is a single solution that can solve all of these issues; and provide you with High Availability AND Disaster Recovery. That solution is SharePlex, Quest' award winning Database Replication software. ShzrePlex replicates your data from one database to a second, reading the Oracle redo log on the source, and applying the changes to the target.
HA and DR - together at last
With SharePlex, there are two (or more) databases, a source, and one or more targets. Since the transfer of data between the two happens over a network, your target database can be in the same data center, across town, or in a data center halfway around the world. That target can serve as both a High Availability solution, and, since it can be located far away, a Disaster Recovery solution as well.
Two databases - no single point of failure
Since the source and target are separate databases, there's no longer a single point of failure. Also, since you have two databases, you can use the second database for reporting. Also, since the target database is open, you always know that your data is available when you need it, SharePlex includes robust compare and repair functions, so you can prove that the source and target databases contain the same data. without having to perform an actual failover and taking down your business critical application.
With some setup, you can even run a "multi-master" solution for workload isolation or load balancing; which will be the subject of the next blog.
Heterogeneous systems? No problem
Since SharePlex performs replication at the database level, it fully supports replication between heterogeneous systems. SharePlex can replicate from Oracle 11 to Oracle 19, or from a Solaris system to a Linux system, or even from an Oracle SE database to an Enterprise Edition database.
Simple setup and management
Above all, SharePlex is simple to install, configure and manage. The same set of binaries are installed on the source and target servers and SharePlex uses one configuration file to manage all replication functions. There's a single command line interface and a no-charge add-on component called SharePlex Manager that gives your a graphical view of your replication environment and sophisticated alerting and alarming if something goes wrong.
Try for yourself
Click here for more information, a demonstration, or to sign up for a free trial in you environment, and stay tuned for the next blog, where we'll cover how SharePlex