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Author's profile photo Laszlo Thoma

Collected information about reclaim / shrink / defragmentation topic in context of SAP HANA persistence (with example)

last updated: 2023-01-16

Introduction

There is huge knowledge available about SAP HANA reclaim / shrink / defragmentation topic, but the knowledge is very fragmented (Help Portal, Blog post, SAP KBA, SAP Note, other). In order to simply and make content consumption easier I have created a centralized page, a single source of the available information regarding SAP HANA persistence. Further I would like to help you with shrinking exercise in SAP HANA, express edition to demonstrate the process.

Task 1. – Exercise

Prerequisites

Background

During the exercises I will use test database SFLIGHT. More information can be find:
SAP HANA, express edition and SFLIGHT demo database, modeling – Complete Tutorial

The SFLIGHT schema is in the Catalog folder.

The actual fragmentation can be identified with the following SQL Statement: “HANA_Disks_Overview”.

  • 1969700 – SQL Statement Collection for SAP HANA
  • 3293572 – SQL Statement Collection: “HANA_Disks_Overview” report for SAP HANA

In production system the fragmentation (~30%) is accepted, should not do reclaim. It will be defragmented to demonstrate the process (test system).

ALTER SYSTEM RECLAIM DATAVOLUME 120 DEFRAGMENT;

The following values (all) had been decreased: TOTAL_GB, UNUSED_GB, FRAG_PCT.

Conclusion

Free up space on DISK level is an easy task in case of SAP HANA. First, we need to identify if there is unused disk space available. When the unused space and the fragmentation details shows we can do the defragmentation. From SAP HANA 2.0 SPS06 this feature had been automated.

Task 2. – Documentation Library

IMPORTANT !
=================================================================

Where to find documentations in SAP Help Portal?

Which is the master SAP Knowledge Base Article of the SAP HANA persistence?

  • 2400005 – FAQ: SAP HANA Persistence

=================================================================

When (in general) and after what action, the fragmentation needs to be checked?

  • 2388483 – How-To: Data Management for Technical Tables
  • 2400024 – How-To: SAP HANA Administration and Monitoring
  • 2718597 – Collection solutions for some big growth tables relevant to HANA DB

Which other documentation is important in context of monitoring SAP HANA persistence?

  • 2988616 – /hana/shared volume full or growing
  • 3054023 – Monitoring hana/data volume growth
  • 3047379 – Monitoring hana/log volume consumption
  • 3195436 – Analyze high disk utilization in HANA Database

Which other documentation is important regarding SAP HANA reclaim / shrink / defragmentation topic?

  • 3194175 – How to reduce table disk size
  • 3265639 – How to reduce History Table size
  • 2910857 – Increase Data Volume free space
  • 2499913 – How to shrink SAP HANA Data Volume size
  • 3272698 – Data volume reclaim in High Availability setup
  • 2984269 – How to cancel DATAVOLUME RECLAIM activity
  • 2815538 – High disk consumption reported under OTHER_GB
  • 2696420 – How to Manually Reclaim LOB space on SAP HANA
  • 3235614 – HANA data volume size increased after table redistribution
  • 3100336 – What is fragmentation in context of SAP HANA persistence?
  • 3198269 – Enable Automatic Data Volume Reclaim in SAP HANA 2 SPS06
  • 2937935 – High disk usage on SAP HANA Data volume caused by technical tables
  • 2348397 – Shrink the Data Volume on Secondary Site with SAP HANA System Replication

Which SAP HANA Alert IDs belongs to the topic?

  • 1870858 – HANA Alerts related to file system utilization

What are the available tools for defragmentation?

The general way to do defragmentation is to use SQL commands. The action can be done in the following way also.

  • SAP HANA Administration with SAP HANA Cockpit – Reclaim Space
  • 2222218 – FAQ: SAP HANA Database Server Management Console (hdbcons)

What is the typical scenario after data deletion?

  • 3209719 – Data file size is not reduced after data deletion.
  • 3202583 – Disk size of the Audit Log table is huge even after clearing

What are the known issues?

  • 2973560 – Data Volume Reclaim Finishes Early
  • 2332284 – Data volume reclaim failed because of snapshot pages
  • 3166382 – Reclaim database space, overhead parameter on SAP HANA
  • 2910343 – SAP HANA data volume reclaim free up less space than expected
  • 2539644 – Reclaim datavolume effected by data backup and System Replication SAP HANA
  • 3202911 – ALTER SYSTEM RECLAIM DATAVOLUME DEFRAGMENT does not release all the expected space

What blog posts can be helpful?

Other articles in this series:

Do you have further questions?

Q&A link for SAP HANA, express edition: https://answers.sap.com/tags/73555000100800000651

Release Information

Release Date Description
2023.01.16 First/initial Release of the SAP Blog Post documentation (Technical Article).

 

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