What happens at HANA System Restart after crash

The SAP HANA system restart sequence is a process that efficiently brings the system back to a fully functional state. Here's a breakdown of the steps involved:

Reading Restart Records:

The restart agent of the persistence layer accesses the data volume of each service to read and load the restart record.

Managing Transactions:

The list of open transactions is read into memory.

Row tables are loaded into memory.

Processing Open Transactions:

Open transactions are processed using the redo log.

Transactions that were open when the database was stopped are rolled back.

Changes to committed transactions that were not written to the data area are rolled forward.

Handling Aborted Transactions:

Aborted transactions are identified and rolled back.

Creating Savepoint:

A savepoint is performed, capturing the restored consistent state of the database.

Column tables that are marked for preload, and their attributes, are asynchronously loaded in the background:

The preload parameter is configured in the meta-data of the table. This feature is useful, for example, to make certain tables and columns that are used by important business processes available more quickly.

Column tables and their attributes that were loaded before restart, start reloading asynchronously in the background (if they have not already been loaded as part of log replay or because they are marked for preload).

In summary, the SAP HANA system restart sequence involves a comprehensive set of steps to ensure a smooth and efficient restoration of the system to a fully operational state, including managing transactions, handling aborted transactions, creating savepoints, and loading tables in a strategic manner.

Note : -

While reloading column tables significantly accelerates the restoration of the database to a fully operational state, it comes with a trade-off in terms of performance overhead. This feature might not be essential for non-production systems. To manage and optimize this process, consider the following configurations:

Deactivation in indexserver.ini:

You have the option to deactivate the reload feature by adjusting the reload_tables parameter in the sql section of the indexserver.ini file. Setting it to "false" turns off the automatic reloading of column tables.

Parallel Loading Configuration:

Adjusting the tables_preloaded_in_parallel parameter in the parallel section of the indexserver.ini file allows you to configure the number of tables whose attributes are loaded in parallel. This setting not only influences the parallel loading of tables during the reload process but also determines the overall performance impact.

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 s...

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 WORKLO...

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 an...

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...

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...

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 HANA System Replication - Operation Mode & Replication Mode

Hey Folks! Welcome back to Hana high availability blog series. In our last blog we checked out what is hana system replication and how it basically works. If you haven't gone through that blog, you can checkout link In this blog we will be talking about the replication modes and operation modes in hana system replication. So let's get started. When we setup the replication and register the secondary site, we need to decide the operation mode & replication mode we want to choose for replication. For now we won't focus on setting up replication as we'll cover it in our next blogs. Operation Modes in Hana System Replication: There are three operation modes available in system replication: delta_datashipping, logreplay and logreplay_readaccess. Default operation mode is logreplay. 1. Delta_datashipping: In this operation mode initially one full data shipping is done as part of replication setup and then a delta data shipping takes place occasionally in addition to cont...

Let's Talk SAP

Search This Blog