SAP HANA System Replication

SAP HANA System Replication - RTO & RPO

In our last blog, we saw what actually is high availability in context of SAP. If you haven't checked it out yet, you can go through this link.

In this blog, we will specifically talk about Hana System replication concept.

What is System Replication?

As we checked, it's a way to achieve high availability in case of outage due to planned maintenance, faults and disasters. It has a very low RTO of few minutes and a RPO of 0 seconds.

RTO - Recovery Time Objective is the time taken to make the secondary/standby system available after the failure of primary system.

RPO - Recovery Point Objective is the difference between the timestamp at which the primary system failed and the timestamp of the latest replicated logs/data available on secondary system.

System replication is supported in every hana installation and can be used for HA as well as DR scenarios.

It is configured as exact copy of the primary system with same number of worker nodes. We can setup multitier system as well by establishing replication between primary to secondary and secondary to dr_site.

When secondary site is located near the primary system, we call the deployment scenario as HA which serve as rapid failover. And when the site is far from primary site, we call that scenario as DR.

The instances in a secondary system operate in recovery mode. In this mode each service establishes a connection with its counterpart and requests a snapshot of the data in the primary system. After that point, all logged changes in the primary system are replicated.
Whenever logs are persisted in the primary system, they are also sent to the secondary system. A transaction in the primary system is not committed until the logs are replicated.

We can configure replication in different types of replication modes. We will cover them in detail in our next blog and will also see what happens in case standby system goes down.

Comments

You might find these interesting

How to properly Start/Stop SAP system through command line ?

Starting/stopping an SAP system is not a critical task, but the method that most of us follow to achieve this is sometimes wrong. A common mistake that most of the SAP admins do is, making use of the 'startsap' and 'stopsap' commands for starting/stopping the system. These commands got deprecated in 2015 because the scripts were not being maintained anymore and SAP recommends not to use them as many people have faced errors while executing those scripts. For more info and the bugs in scripts, you can check the sap note 809477. These scripts are not available in kernel version 7.73 and later. So if these are not the correct commands, then how to start/stop the sap system? In this post, we will see how to do it in the correct way. SAP SYSTEM VS INSTANCE In SAP, an instance is a group of resources such as memory, work processes and so on, usually in support of a single application server or database server with

sapstartsrv is not started or sapcontrol is not working

What is sapstartsrv ? The SAP start service runs on every computer where an instance of an SAP system is started. It is implemented as a service on Windows, and as a daemon on UNIX. The process is called sapstartsrv.exe on Windows, and sapstartsrv on UNIX platforms. The SAP start service provides the following functions for monitoring SAP systems, instances, and processes. Starting and stopping Monitoring the runtime state Reading logs, traces, and configuration files Technical information, such as network ports, active sessions, thread lists, etc. These services are provided on SAPControl SOAP Web Service, and used by SAP monitoring tools (SAP Management Console, SAP NetWeaver Administrator, etc.). For more understanding use this link : https://help.sap.com/doc/saphelp_nw73ehp1/7.31.19/enUS/b3/903925c34a45e28a2861b59c3c5623/content.htm?no_cache=true How to check if it is working or not ? In case of linux , you can simply ps -ef | grep sapstartsrv In case of windows, you need

HANA System Replication - Prerequisites & Setup

Hey Folks! Welcome back to Hana high availability blog series. In our last blog we checked out operation & replication modes in hana system replication. If you haven't gone though that blog, you can checkout this link In this blog we will be talking about the prerequisites of hana replication and it's setup. So let's get started. When we plan to setup hana system replication, we need to make sure that all prerequisite steps have been followed. Let's have a look at these prerequisites. HANA System Replication Prerequisites: Primary & secondary systems should be up & running HDB version of secondary should be greater than or equal to Primary database sever But, for Active/Active(read enabled config), HDB version should be same on both sites. System configuration/ini files should be identical on both sides Replication happe

HANA hdbuserstore

The hdbuserstore (hana secure user store) is a tool which comes as an executable with the SAP Hana Client package. This secure user store allows you to store SAP HANA connection information, including user passwords, securely on clients. With the help of secure store, the client applications can connect to SAP HANA without the user having to enter host name or logon credentials. You can also use the secure store to configure failover support for application servers in a 3-tier scenario (for example, SAP Business Warehouse) by storing a list of all the hosts that the application server can connect to. To access the system using secure store, there are two connect options: (1)key and (2)virtualHostName. key is the hdbuserstore key that you use to connect to SAP HANA, while virtualHostName specifies the virtual host name. This option allows you to change where the hdbuserstore searches for the data and key files. Note

ST03N : The chapter for all BASIS Admins

This blog is targeted to BASIS ADMINS Transaction for workload analysis statistical data changed over time are monitored using transaction code ST03 , now ST03N (from SAP R/3 4.6C) . With SAP Web AS 6.4 the transaction ST03 is available again. From time to time ST03 and ST03N has seen many changes but later in SAP NW7.0 ST03N has reworked in detail specially processing time is now shown in separate column. Main Use of ST03N is to get detailed information on performance of any ABAP based SAP system. Workload monitor analyzes the statistical data originally collected by kernel. You can compare or analyze the performance of a single application server or multiple application server. Using this you start checking from the entire system and finding your way to that one application server and narrowing down to exact issue. By Default :- You see data of current day as default view , you can change the default view. Source of the image : sap-perf.ca Let's discuss the WORKLOAD MONITOR By D

Work Process and Memory Management in SAP

Let’s talk about the entire concepts that are related to memory when we talk about SAP Application. Starting with few basic terminologies, Local Memory : Local process memory, the operating system keeps the two allocation steps transparent. The operating system does the other tasks, such as reserving physical memory, loading and unloading virtual memory into and out of the main memory. Shared Memory : If several processes are to access the same memory area, the two allocation steps are not transparent. One object is created that represents the physical memory and can be used by various processes. The processes can map the object fully or partially into the address space. The way this is done varies from platform to platform. Memory mapped files, unnamed mapped files, and shared memory are used. Extended Memory : SAP extended memory is the core of the SAP memory management system. Each SAP work process has a part reserved in its virtual address space for extended memory. You can set

ABAP Dumps Analysis

Ever now and then have you heard about ABAP Dumps, We also have a joke everything in temporary in life except ABAP dumps for SAP Consultants. Lets try to understand ABAP dumps from perspective of a SAP BASIS Consultant. Dumps happen when an ABAP program runs and something goes wrong that cannot be handled by the program We have two broad categories of Dumps , In custom program Dumps and SAP provided program Dumps. Dumps that happen in the customer namespace ranges (i.e. own-developed code) or known as Custom Program , can usually be fixed by the ABAP programmer of your team. Dumps that happen in SAP standard code probably need a fix from SAP. You do not have to be an "ABAPer" in order to resolve ABAP dump issues. The common way to deal with them is to look up in ST22 How to correct the error ? Hints are given for the keywords that may be used to search on the note system. Gather Information about the issue Go to System > Status and Check the Basis SP level as well as info

How to resolve Common Error : Standard Template "sap_sm.xls" missing

Hey everyone, putting forward a common error we usually face when we have “ Excel inplace” functionality enabled in our SAP system. This error occurs when validity of the signature of SAP standard templates expired or were incorrectly delivered via support packages. We can reproduce the error by doing as below.. Click on “spreadsheet” icon after any SAP ALV grid view of data is on screen to make this data to export into excel directly from SAP.

SAP application log tables: BALHDR (Application Log: Header Data) and BALDAT (Application Log: Detail Data)

BALHDR (Application Log: Header Data): Usage : The BALHDR table stores the header information for application logs. It serves as a central repository for managing and organizing log entries. Example Data Stored: The table may contain entries for various system activities, such as error messages, warnings, or information logs generated during SAP transactions or custom programs. Columns Involved: LOGNUMBER: Unique log number assigned to each log entry. OBJECT: Identifies the object associated with the log entry (e.g., a program, transaction, or process). SUBOBJECT: Further categorizes the object. USERNAME: User ID of the person who created the log entry. TIME: Date and time when the log entry was created. ADD_OBJECT: Additional information or details related to the log entry. BALDAT (Application Log: Detail Data): Usage : The BALDAT table contains the detailed data for each log entry, linked to the corresponding entry in the BALHDR table. It stores the specific log details and me

"DST Switch" - All you need to know about Daylight Saving Time Switch in SAP

Daylight Saving Time(DST) : DST is the practice of advancing clocks during part of the year, typically by one hour around spring and summer , so that daylight ends at a later time of the day. How SAP systems are affected due to DST : Many kinds of software that deal with local time, such as the SAP system, have serious problems in this hour, because operations which use local times can fail if time does not increase continuously, and points in time can "happen" twice. Double Hour Concept : In many northern hemisphere countries (i.e., Europe: European Union, Russia; North America: USA, Canada, Mexico) At the end of daylight-saving period, one hour occurs twice as the clocks are put back an hour. In Europe, for example, this hour is between 2:00 a.m. and 3:00 a.m., whereas in the USA it occurs between 1:00 a.m. and 2:00 a.m. This means that the clock will move twice in the same day from 1am to 2am. Double hour refers to the duration of the hour that the cloc

Let's Talk SAP

Search This Blog