What's new on SAP HANA Workload Management

1© 2015 SAP SE or an SAP affiliate company. All rights reserved. 1© 2014 SAP AG or an SAP affiliate company. All rights reserved.
SAP HANA SPS 11 - What’s New?
Workload Management
SAP HANA Product Management December, 2015
(Delta from SPS 10 to SPS 11)

© 2015 SAP SE or an SAP affiliate company. All rights reserved. 2Public
Agenda
Introduction
 What is Workload Management ?
Strategies to handle mixed workload
 Thread Pool Sizes
 Memory Consumption Limit
 Degree of Parallelism and Execution Priority
Dynamic Workload Mapping
 Workload Classes and Workload Mapping
 Monitoring
Customer Feedback
Summary

Mixed Workload in the Context of SAP HANA
Workload is a set of requests with common characteristics, e.g.
 Source of request (user, application)
 Query types (ad-hoc, batch, analytical, transactional)
 Business importance (high, low, best effort)
 System Level Objectives (SLOs), e.g. response time, throughput
Workload has certain resource demands to the system, e.g.
 CPU
 Memory
 Disk I/O
 Network bandwidth
Mixed workloads compete for shared system resources
 If a request consumes a significant amount of system resources, other requests are subject
queuing effect
 Waiting workloads fail to meet their expected performance
 Overall system performance degradation may occur
DRAM DRAM DRAM
SQL SQL SQL
ETL Analytics Transactions

What is Workload Management ?
Objectives
 Runs the database in an optimal resource state
 Maximize overall system performance
 Balance resource demand between workloads
 Ensures that request meet their required SLOs
 Continuous maintenance and improvement of overall
workload efficacy, in an iterative manner
Understand your Workload
Business Importance
Application Type
Query Types
Resource Demand
Users
Conflicts between Workloads
Map your Workload to System
Resources
CPU
Memory
Priority
Degree of Parallelism
Workload Classes
Analyze System Performance
CPU utilization
Memory consumption
Expensive Statements (Memory)
Over-Parallelization
Workload-
Management
Process

Strategies to handle mixed
workloads

Thread Pools Sizes
Defintion:
Thread Pools are managed inside of the HANA database per index server and provide
the ability to expand or throttle how much of available CPU SAP HANA can consume
HANA Thread-Pools
 Job-worker thread pool  Job Executor
 Request thread pool  SQL Executor
Job Executor
 Handles complex, long-running statements (typically OLAP-like)
 Manages job queues (1-2 per CPU)
 Configure the thread pool size
– global.ini -> execution -> max_concurrency
SQL Executor
 Handles simple, short-running statements (typically OLTP-like)
 Configure the thread pool size
– indexserver.ini -> sql -> sql_executors
– indexserver.ini -> sql -> max_sql_executors
SQL SQL
OLAP OLTP
SAP HANA
(indexserver)
max_concurrency max_sql_executor
Key Point – max concurrency
parameter: control overall number of
threads that can be busy at any one
time for complex operations (1
thread equates to 1 logical core)

Memory Consumption Limit
Global memory allocation limit per database (GAL)
 Max amount of memory that can be used by the database
– global.ini -> memorymanager -> global_allocation limit = <MB>
 Default: 90% of physical memory
Memory allocation limit per statement
 Max amount of memory that can be used by a single statement
– global.ini -> memorymanager -> statement_memory_limit = <GB>
 Default: 0 <unlimited>
Memory limit threshold per statement
 Controls if/when parameter statement_memory_limit is applied;
 Statement memory limit s applied only if total memory (for a particular statement) exceeds the global allocation limit by the value derived by the
statement_memory_limit_threshold (as a percentage of global_allocation_limit)
 Means of ensuring an inordinate amount of memory is not consumed by a single statement
– global.ini -> memorymanager -> statement_memory_limit_threshold = <%>
 Default: 0%, i.e. statement_memory_limit is always applied

Degree of Parallelism and Execution Priority
Parallel Execution
 SAP HANA , as much as it possibly can, executes with maximum parallelization in an automated manner -> highest system performance
 SAP HANA auto-determines degree of parallel statement execution (execution plan, job graph)
Degree of Parallelism
 Default: unlimited use of threads for parallel statement execution (best effort)
 Can be controlled by statement thread limit per statement in workload classes
 Default parallel degree can be controlled with parameter default_statement_concurrency_limit
– e.g. settting value to 8 means max 8 threads can be engaged at any one time for any one statement
Execution Priority
 is applied to jobs of the Job Executor
 all generated jobs for a statement get an “external priority”
 execution priority for all statements per user can be set between 0 … 9; default is 5
 Syntax:
– alter user SYSTEM set parameter PRIORITY = '9';
– select priority from m_connections where connection_id = CURRENT_CONNECTION;
New for SPS11

What is Dynamic Workload Mapping ?
Motivation
 System-wide resource settings are static and does not fit to all workloads
 Manual admin tasks to set parameter for every workload and user are error prone and complex
Objectives
 Dynamic mapping of system resources to DB-clients with different workload profiles
 Flexible resource mapping on session and statement granularity
 Focus on avoiding severe resource abuse by single statements vs. resource pre-allocation
 No changes in the application code of the DB-clients

Workload Mapping
Desktop Datamart
Administrator Tasks:
• create workload classes
• define mapping rules
Mobile Dashboard
db-connect
SAP HANA Session Layer
Workload Class
“DATAMART”
db-connect
session
context
Workload Class
“BW”
Workload Class
“CRM”
Workload Class
“MOBILE”
Mapping
Rules
session
context

Defining Workload Classes
Workload Classes represent individual and named sets of resource properties
 statement thread limit = max #of parallel threads to execute a statement
 statement memory limit = max #of memory allocated per statement
 statement priority = execution priority for a statement
SQL Syntax: <CREATE|ALTER|DROP> WORKLOAD CLASS <NAME> [SET|UNSET <PROPERTY LIST>]
Example: create workload class “DATAMART" set 'PRIORITY' = '6', 'STATEMENT MEMORY LIMIT' = '2','STATEMENT THREAD LIMIT' = '8‘;
Note
 You can define all resource properties or only a subset in a workload class
 Workload Class definitions can be checked in the HANA system view WORKLOAD_CLASSES
– select * from workload_classes;

Defining Mapping Rules
The HANA session layer reads the client context information
 application name = name of the application
 application user name = name of the application user (usually the user logged into the application)
 user name = name of the db-user (where the application is connected with HANA technically)
 client = ABAP client number (“mandant”) or can be used for setting
SQL Syntax: <CREATE|ALTER|DROP> WORKLOAD MAPPING <NAME> WORKLOAD CLASS <WC NAME> [SET <PROPERTY LIST>]
Example: create workload mapping “BICLIENT" workload class “DATAMART" set 'USER NAME' = ‘DATA001‘;
Note
 You can define all client context information as mapping attributes or only a subset
 Workload Mapping definitions can be checked in the HANA system view WORKLOAD_MAPPINGS
– select * from workload_mappings;

Monitoring Views for Workload Mapping
 SYS.M_CONNECTIONS_, SYS.M_PREPARED_STATEMENTS_; SYS.M_ACTIVE_STATEMENTS_
 global.ini-> resource_tracking -> enable_tracking = on / memory_tracking = on

Additional Remarks about Workload Classes - 1 -
Privileges
 Managing workload classes requires the ‘WORKLOAD ADMIN’ privilege
Changing Workload Classes
 Changes of workload classes or mappings will only be applied, if a (connected) db-client re-connects
 You can change the running session-context of a connected db-client via SQL-command ‘ALTER SYSTEM
ALTER SESSION SET‘ (not recommended)
Multi-Database Containers (MDC)
 Workload classes work also in a multi-database environment, but you need to define workload classes for each
single db-container
Scale-out
 Workload classes are applied to the complete HANA-db in a scale-out environment, but not to each single node

Additional Remarks about Workload Classes – 2-
Dropping users / workload classes
 If you drop a user in the HANA-db, all related workload classes are dropped
 If you drop a workload class, the related mappings are dropped
Setting the client context in the application
 The client info object contains the client context information as key/value pairs
 The ABAP Server sets the client context information automatically for all ABAP applications
 The client interface of the corresponding driver (jdbc/odbc/python) provides methods to set client info object
properties (see SAP note 2215929)
 New for SPS11: Setting Session-Specific Client Information is now documented in the SAP HANA Developer
Guide (see section 12.1)

Customer POC Scenario:
How SAP HANA WLM helps web requests in peak load situations
Description
 This scenario is done to capture how WLM helps web requests in peak load situations
 Captures the impact of other workloads on the web request with workload class and with out workload class
 Started 50 web request/second and kept it constant and slowly increase analytical and ETL load by adding 5 every 5 minutes.
 Stressed the system CPU utilization to Max and CPU was showing 100% most of the time
Workload Class Specification
 Web User ( no limitation on resource)
 ETL User ( Threads limited to 1 and memory limit to 5 GB per sql)
 ANALYTIC User ( Threads limited to 1 per SQL and memory limit 5GB per sql)

Results
Outcome
 There is huge difference in hits per seconds
of the web request with workload class and
with out workload class
 Response times are stable even after
increasing load from other low priority
workloads.
Hits /Second Without WLM With WLM
MIN 0 6.922
AVG 71.641 152.010
MAX 94.406 157.297

Summary
 SAP HANA is a database platform to run various applications with different workload profiles on the same data
 SAP HANA provides various strategies to manage and balance resources between applications
 Thread Pool Sizes
 Memory Allocation Limits
 Degree of Parallel Execution
 Execution Priorities
 SAP HANA provides a dynamic workload mapping to manage resources on statement and session level
 SAP HANA Workload Management is an ongoing development effort
 For more details on SAP HANA Workload Management see: SAP TechEd 2015 Video – Workload Management

Disclaimer
This presentation outlines our general product direction and should not be relied on in making
a purchase decision. This presentation is not subject to your license agreement or any other
agreement with SAP.
SAP has no obligation to pursue any course of business outlined in this presentation or to
develop or release any functionality mentioned in this presentation. This presentation and
SAP’s strategy and possible future developments are subject to change and may be changed
by SAP at any time for any reason without notice.
This document is provided without a warranty of any kind, either express or implied, including
but not limited to, the implied warranties of merchantability, fitness for a particular purpose, or
non-infringement. SAP assumes no responsibility for errors or omissions in this document,
except if such damages were caused by SAP intentionally or grossly negligent.

© 2015 SAP SE or an SAP affiliate company. All rights reserved.© 2014 SAP AG or an SAP affiliate company. All rights reserved.
Thank you
Contact information
Ruediger Karl / Ron Silberstein
SAP HANA Product Management
AskSAPHANA@sap.com

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