availability (2)

With the advancements in DB2 server clustering technologies (both Sysplex and pureScale) and the DB2 Connect client drivers, it is now possible to achieve near continuous application availability. Availability is now no longer about only database server availability, but there is more focus on availability of applications that access the data stored on the server. Having the server up and running is not very meaningful if the applications connected to the server suffer connection failures and downtime. And customers rightfully have come to expect that their local and distributed applications originating from around the world, stay up and running 24X7.

DB2 Connect client driver availability technology has grown leaps and bounds over the last few years – this ensures that applications continue to function in case of server unplanned outages as well as planned outages such as rolling upgrades when members of a DB2 cluster are migrated one by one. Client driver availability algorithms complement server availability technologies to ensure highest availability in a distributed environment. A combination of features around workload balancing and failover have been built into DB2 Connect client drivers. While workload balancing achieves higher throughput by distributing connections and transactions to members with maximum capacity at any point in time, failover reconnects applications to next best available member in case of a connection failure.

In recent releases of DB2 Connect, default values of properties that determine high availability behavior have been changed to values that work well out of the box for majority of customers. Given the number of products in the DB2 stack (application server, client driver, DB2) and myriad high availability knobs at each layer, customers found it difficult to achieve an optimal end-to-end configuration leading to outages that could have been avoided in the fist place. Default value changes also control resource consumption and allow faster recovery from failover. For example, the default value of maxTransportObjets was changed from -1 (unlimited connections) to a more reasonable value of 1000, that prevents runaway applications from creating too many unnecessary connections and deplete system resources.

Number of features were added for easier problem determination in complex high availability setups. For eg, new statistics were introduced to better manage socket connections to clustered DB2. More details were added to the errors that are returned to the application going against a cluster – that provide the application more information on what kind of failover happened and whether the application needs to take further action for a successful transaction. For eg, reason codes and detailed message texts were added to the -30108 error that notifies the application that the transaction did not qualify for a seamless reroute to another DB2 member and that the application should resubmit the transaction for the reroute to occur.

High availability technologies built into the DB2 server and DB2 Connect client drivers complement each other and together have come a long way to satisfy customer's needs for continuous availability of business critical data and applications. To get the most availability for distributed applications, we do recommend you to upgrade DB2 Connect client drivers to the latest available levels.
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Consider direct distributed connections to DB2 and trading up to DB2 Connect Unlimited Edition  by Pallavi Priyadarshini

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Top banks, financial services, retail and telecom companies store their mission critical data on  DB2 for z/OS, DB2 LUW and DB2 for i. Distributed workloads accessing DB2 data have proliferated due to the ubiquity of Web and Mobile applications. DB2 Connect provides a portfolio of database drivers offering distributed access to DB2 data through standard interfaces such as JDBC, SQLJ, OLE DB, ADO, ADO.NET, CLI, embedded SQL and scripting Languages such as PhP, Python, Ruby and Perl.

For distributed access to data stored on DB2 for z/OS and DB2 for i, license entitlement to DB2 Connect must be purchased. DB2 Connect is offered in several editions (Enterprise Edition, Application Server Edition, Unlimited Edition). Introduction of Unlimited Edition for both DB2 for z/OS and DB2 for i offers flexibility for direct connections to DB2 servers (without the DB2 Connect Server or Gateway) and transparently handles growth in number of users and applications. More customers anticipate the need for more users accessing DB2 data from Web, Mobile and Cloud anytime, anywhere. DB2 Connect Unlimited Edition license charges are not based on number of users or application servers, rather it is based off the processing capacity of zSeries and iSeries servers. This allows any number of distributed users, applications and workstations to connect. It also allows server side install of DB2 Connect license, instead of replicating the license on potentially hundreds of client workstations or application servers.

We are seeing a pattern whereby the decision to trade up to DB2 Connect Unlimited Edition is taken when customers adopt direct connectivity to DB2 servers (without the DB2 Connect Server or Gateway component). With the advancements in DB2 Connect client drivers around connection management, failover and workload management, more customers are adopting direct distributed connectivity to DB2 instead of going through the DB2 Connect Server or Gateway component. Direct connections to DB2 offers several advantages -

1) Simplification of distributed connectivity by reduction of one layer.
2)  Reduced resource consumption since no resources for DB2 Connect Server machines  (hardware, software) needed. No installation, maintenance, migration of this extra component.
3) Improved availability as point of failure is removed.     

4)  Improved response time of distributed applications (especially OLTP applications) due to elimination of extra hop.
We encourage you to evaluate simplification of DB2 Connect environment by going direct to DB2 (without Gateway) and upgrading to Unlimited Edition. You will not have to worry about growing number of users and applications who become instantly available without any prior notice from different channels such as Web, Mobile and Cloud.

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