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## 1 SAP HANA Troubleshooting and Performance Analysis Guide	## 1 SAP HANA Troubleshooting and Performance Analysis Guide With SAP HANA, you can analyze data at incredible speeds, for example, with scans of 1 billion rows per second per core and join performance of 10 million rows per second. However, such results are only possible if the system is monitored and performance issu...
## 2 Analyzing Generic Symptoms	## 2 Analyzing Generic Symptoms The purpose of this section of the document is to help you to find the probable root cause of some generic problems and refer you to more detailed sections of the SAP HANA Troubleshooting and Performance Analysis Guide to proceed with your analysis. Performance issues may be difficult to...
## 2.1 Using the SQL Statement Collection for Analysis and Health Checks	## 2.1 Using the SQL Statement Collection for Analysis and Health Checks A collection of predefined customizable statements is available for checking the database. An extensive SQL statement collection is available for analyzing the SAP HANA database, this can be used to examine specific problems or for routine monitor...
## 2.2 Handling SQL Errors	## 2.2 Handling SQL Errors Errors generated when executing SQL statements are identified by a code number which may be helpful to find an explanation and solution to the problem. This section gives some recommended solutions to help solve problems related to SQL errors. The topic which follows 'SQL Error Reference' is ...
## 2.2.1 SQL Error Reference	## 2.2.1 SQL Error Reference The following reference table provides links to sources of troubleshooting information for many frequently occurring SQL errors. SQL Error Codes \| Code \| Type \| Description \| More information ...
## 2.3 Performance and High Resource Utilization	## 2.3 Performance and High Resource Utilization By observing the general symptoms shown by the system such as poor performance, high memory usage, paging or column store unloads we can start to narrow down the possible causes as a first step in analyzing the issue. ## High Memory Consumption You observe that the amoun...
## 2.4 Common Symptoms and Troubleshooting	## 2.4 Common Symptoms and Troubleshooting Typical symptoms and the related troubleshooting information are described in this section. System-side slow performance, slow individual statement performance, and OOM problems are issues that you might experience while using the SAP HANA database. For each section, this docu...
## 2.4.1 Slow System-wide Performance	## 2.4.1 Slow System-wide Performance Slow system-wide performance issues are problems that could be caused by excessive use of CPU, database resource locks or incorrect configuration of OS parameters. Generally, when you encounter a performance issue, you may see these symptoms in SAP HANA cockpit: - Continually high...
## 2.4.1.1 HANA System-wide Performance Analysis	## 2.4.1.1 HANA System-wide Performance Analysis This topic describes solutions for both current and former system performance problems. ## Analysis of Current Performance Problems Before taking any other action while the problem is present it is of utmost importance to capture a few HANA runtime environment (RTE) dump...
## 2.4.1.2 System Appears to Hang with no new Connections and no Response from the SAP HANA Database	## 2.4.1.2 System Appears to Hang with no new Connections and no Response from the SAP HANA Database In cases where logs cannot be written, all DML statement will fall into wait status. This can lead to a failure of opening new connections because the system internally executes DML statements during the process. Typica...
## 2.4.1.3 System Appears to Hang with High System CPU Usage	## 2.4.1.3 System Appears to Hang with High System CPU Usage The SAP HANA database is an in-memory database and by its nature it consumes large amounts of memory. Some performance issues of SAP HANA can be caused by the operating system's memory management features. For this case, you can see high usage of SYSTEM CPU t...
## 2.4.1.4 Slower Response with High User CPU Usage	## 2.4.1.4 Slower Response with High User CPU Usage The performance may degrade with increased usage of the CPU and applications. Root cause: Not many executor threads but high CPU in a few nodes and a few tables accessed Required Action: In an SAP Business Warehouse system, check for non-even partitioning of huge colu...
## 2.4.2 Slow Individual SQL Statements	## 2.4.2 Slow Individual SQL Statements This section looks at the causes of slow individual SQL statements although there is no significant performance issue on system level and the associated troubleshooting steps. If the following doesn't help to resolve the problem, see Getting Support . In this case, to analyze fu...
## 2.4.2.1 A Statement is Sometimes Slow and Sometimes Fast	## 2.4.2.1 A Statement is Sometimes Slow and Sometimes Fast There are a number of things to check when you experience inconsistent query execution time. Check the following possibilities: Root Cause: Same query shows different execution plans according to the HANA SQL Plan Cache. Required Action: Analyze the difference...
## 2.4.2.2 A Statement is Slower After an Upgrade	## 2.4.2.2 A Statement is Slower After an Upgrade After upgrade, the query execution time can be different because of changes in the query execution plan. Root cause: After an upgrade, a query can have a different plan, which leads to a different execution time. Required Action: If you have an instance running on an ol...
## 2.4.2.3 A Query on Multiple Nodes Can Be Slower	## 2.4.2.3 A Query on Multiple Nodes Can Be Slower In distributed systems, query execution can be routed to other nodes for better performance. However, there is a chance of having slow performance in the case where the network used for transferring intermediate results generated during query execution is slow or where...
## 2.4.2.4 Slow Select for all Entries (FAE) Query	## 2.4.2.4 Slow Select for all Entries (FAE) Query There are a number of points to check if you have performance issues with SELECT FOR ALL ENTRIES (FAE) from an ABAP query. For FAE on SAP HANA, please generally refer to SAP Note 1662726 - Optimization of select with FOR ALL ENTRIES on SAP HANA database . Root cause: I...
## 2.4.2.5 All Statements Accessing a Specific Table are Slow	## 2.4.2.5 All Statements Accessing a Specific Table are Slow In case queries run on specific tables are slow, check if there are too many versions. Root cause: If there are too many versions of single records, accessing the table can be slow. In this case, the number of system-wide MVCC versions is in acceptable range...
## 2.4.3 Frequent Out of Memory (OOM)	## 2.4.3 Frequent Out of Memory (OOM) If Out Of Memory situations happen frequently, it can also lead to performance drop by unloading tables or shrinking memory jobs. First check Memory Problems and SAP KBA 1999997 - FAQ: SAP HANA Memory as they provide information on SAP HANA memory and its problems. This section in...
## 2.4.3.1 Out of Memory Caused by Sudden Increased Memory Usage	## 2.4.3.1 Out of Memory Caused by Sudden Increased Memory Usage Check the memory consumption of statements in the event of OOMs caused by suddenly increased memory usage. Root cause : Huge intermediate results during query processing. Required Actions: Enable memory tracking by setting the following parameters to on i...
## 2.4.3.2 Out of Memory Caused by Continuously Increased Memory Usage	## 2.4.3.2 Out of Memory Caused by Continuously Increased Memory Usage Check if many statements trigger an Out Of Memory in a system where used memory is continuously increased. Root cause: Commit/rollback within stored procedure can lead to memory leakages. Do not use exec('commit') or exec('rollback') within a stored...
## 2.4.3.3 Out of Memory While High Usage Of Column Store Components' Allocators	## 2.4.3.3 Out of Memory While High Usage Of Column Store Components' Allocators If a system is undersized, Out Of Memory (OOM) can happen frequently. Root cause: Undersized memory ## Required Action: 1. Check top allocators in [MEMORY_OOM] section of OOM dump to see whether they are for column store components as desc...
## 2.4.3.4 Out of Memory Caused by Large Memory Usage of Statistics Server	## 2.4.3.4 Out of Memory Caused by Large Memory Usage of Statistics Server This case can happen if the majority of memory used by the statisticsserver is due to many alerts or undersized memory. Root cause: Due to big STATISTICS_ALERTS_BASE table size, an OOM can occur. Required Action: Check table size of _SYS_STATIST...
## 2.4.3.5 Out of Memory Occurs due to High Usage of Shared Memory	## 2.4.3.5 Out of Memory Occurs due to High Usage of Shared Memory Shared memory is space where system information and row store tables are stored. Check the following if the used amount of shared memory is high. Root cause: Severely fragmented row store tables ## Required action: 1. Check whether SHARED_MEMORY in [MEM...
## 2.4.4 Table Consistency Check	## 2.4.4 Table Consistency Check This section gives basic information for solving problems related to the Table Consistency Check. The table consistency check is a procedure available in the SAP HANA database that performs a range of consistency check actions on database tables. It can be run from the command line or ...
## 3 Root Causes and Solutions	## 3 Root Causes and Solutions This section provides detailed information on the root causes of problems and their solutions. System alerts are a good indicator for the underlying problem. The SAP Notes you will be directed to are a source of background information, explanations, alternative options, FAQs or useful SQL...
## 3.1 Memory Problems	## 3.1 Memory Problems This section discusses the analysis steps that are required to identify and resolve memory related issues in the SAP HANA database. For general information on SAP HANA memory management see the SAP HANA Academy video SAP HANA Memory Management which discusses the memory concept and comments on th...
## 3.1.1 Memory Information in SAP HANA Cockpit	## 3.1.1 Memory Information in SAP HANA Cockpit There are a number of sources of information in SAP HANA cockpit that can assist you in understanding memory utilization. - Open the Manage Services page from the Overall Database Status tile for high-level information about physical memory, allocation limit, and used me...
## 3.1.2 Memory Information from Logs and Traces	## 3.1.2 Memory Information from Logs and Traces In case of critical memory issues you can often find more detailed information in logs and trace files. - Try to identify memory-related errors in the alert trace files in the SAP HANA database explorer (accessible via the View trace and diagnostic files link). Search f...
## 3.1.3 Memory Information from SQL Commands	## 3.1.3 Memory Information from SQL Commands There are a number of ways to analyze memory usage based on pre-defined and modifiable SQL queries. The Statement Library of SAP HANA database explorer provides a set of tabular views to display the memory consumption of loaded tables based on pre-defined SQL queries: - Th...
## 3.1.4 Memory Information from Other Tools	## 3.1.4 Memory Information from Other Tools Other tools are also available to analyze high memory consumption and out-of-memory situations. A number of SAP Notes and 'How-to' documents are available to provide help with some of the most common questions and difficulties related to memory. The tool hdbcons provides ex...
## 3.1.5 Root Causes of Memory Problems	## 3.1.5 Root Causes of Memory Problems Once you have completed your initial analysis, you have the information required to start the next phase of your analysis. Based on the results from the analysis approaches you are now able to answer the following questions: - Is it a permanent or a sporadic problem? - Is the me...
## 3.1.5.1 Significant External Memory Consumption	## 3.1.5.1 Significant External Memory Consumption If the database resident memory of all SAP HANA databases on the same host is significantly smaller than the total resident memory, you have to check which processes outside of the SAP HANA databases are responsible for the additional memory requirements. Typical memor...
## 3.1.5.2 Space Consumed by Large Tables	## 3.1.5.2 Space Consumed by Large Tables If particularly large tables consume significant amounts of space in the row store or column store, you should check if the amount of data can be reduced. The following references will be helpful: - SAP Note 2388483 - How To: Data Management for Technical Tables describes archi...
## 3.1.5.3 Internal Columns in the Column Store	## 3.1.5.3 Internal Columns in the Column Store For several reasons, SAP HANA creates internal columns in the column store. Some column store tables are automatically loaded into memory. ## Internal Columns You may be able to optimize or remove internal columns in order to reduce memory usage. In some situations a clea...
## 3.1.5.4 Memory Leaks	## 3.1.5.4 Memory Leaks A memory leak is a memory area (typically a heap allocator) that grows over time without any apparent reason. If you have identified a suspicious area, proceed as follows: - Check for SAP Notes that describe the memory leak and provide a solution. - Check if the problem is reproducible with a re...
## 3.1.5.5 Large Heap Areas	## 3.1.5.5 Large Heap Areas Some heap areas can be larger than necessary without being a memory leak. SAP Note 1840954 - Alerts Related to HANA Memory Consumption contains an overview of heap allocators with a potentially large memory consumption and possible resolutions. Refer also to SAP Note 1999997 - FAQ: SAP HANA ...
## 3.1.5.6 Expensive SQL Statements	## 3.1.5.6 Expensive SQL Statements SQL statements processing a high amount of data or using inefficient processing strategies can be responsible for increased memory requirements. See SQL Statement Analysis for information on how to analyze expensive SQL statements during times of peak memory requirements. ## Related ...
## 3.1.5.7 Memory Consumption Related to Transactional Problems	## 3.1.5.7 Memory Consumption Related to Transactional Problems High memory consumption can be caused by problems with transactions. In some cases, high memory consumption is caused by wait situations, which can have different reasons: - Long-running or unclosed cursors, - Blocked transactions, - Hanging threads. As on...
## 3.1.5.8 Used Space Much Smaller than Allocated Space	## 3.1.5.8 Used Space Much Smaller than Allocated Space In order to optimize performance by minimizing the memory management overhead or due to fragmentation, SAP HANA may allocate additional memory rather than reusing free space within the already allocated memory. This can lead to undesired effects that the SAP HANA ...