[IQUG] [iqug] IQ SYSTEM MAIN filling up during FULL backups

Louie, David David.Louie at blackrock.com
Mon Mar 4 09:51:07 MST 2019

Thanks Mark.

The requirement has really gone up.  So for my 45 TB server I’d need at least 1250 GB of SYSTEM MAIN.

It will be a challenge to  I explain the sudden need to get to this recommended size when we were well below the required space for the longest time.

But we have had two instances on separate systems where during backups we exhausted SYS MAIN.

It will be interesting to know if any other shops are keeping up with the required space for SYS MAIN.


From: Mumy, Mark [mailto:mark.mumy at sap.com]
Sent: Monday, March 04, 2019 11:37 AM
To: Louie, David <David.Louie at blackrock.com>; iqug at dssolutions.com
Subject: Re: [IQUG] [iqug] IQ SYSTEM MAIN filling up during FULL backups

External Email: Use caution with links and attachments

This is from my most recent sizing guide (https://www.sap.com/documents/2017/02/363ddfab-a77c-0010-82c7-eda71af511fa.html):

Sizing the default main store (IQ_SYSTEM_MAIN) is relatively straightforward and based on the size of the user defined dbspaces, in total, as well as the number of nodes in the multiplex.

For databases that are less than 1 TB, it is recommended that IQ_SYSTEM_MAIN be 15-20% of the user defined main space size, with a minimum of 32 GB.  If this instance is migrated to a multiplex, an additional 10 GB of space should be added per node in the multiplex.  For a 2 node system with a 100 GB database, the size would then be 52 GB (32GB base + 10 GB per node).

For databases that exceed 1 TB, it is recommended that IQ_SYSTEM_MAIN be at least 150 GB plus 10 GB for every additional TB.  A 10 TB database would require 250 GB of IQ_SYSTEM_MAIN (150 + 10*10)

For a multiplex, an additionally 10 GB of space should be allocated for each node of the multiplex.  For a 4 node system with a 10 TB database, you would need 290 GB of system main =(150 GB + 10TB*10GB per TB + 4 nodes*10GB each).

The system main size is based on the total defined user main spaced, not just the % in use.  And yes, it must be resized as you add storage over time (or compensate for that up front by having a larger system main).


Mark Mumy
Strategic Technology Incubation Group
SAP Global Center of Excellence |  SAP
M +1 347-820-2136 | E mark.mumy at sap.com<mailto:mark.mumy at sap.com>
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From: "iqug-bounces at iqug.org<mailto:iqug-bounces at iqug.org>" <iqug-bounces at iqug.org<mailto:iqug-bounces at iqug.org>> on behalf of David Louie <David.Louie at blackrock.com<mailto:David.Louie at blackrock.com>>
Date: Monday, March 4, 2019 at 6:22 PM
To: IQ Group <iqug at dssolutions.com<mailto:iqug at dssolutions.com>>
Subject: [IQUG] [iqug] IQ SYSTEM MAIN filling up during FULL backups


Recently on several IQ 15.4 and 16.0 servers we have been filling up IQ SYSTEM MAIN which caused the server to stacktrace and crash during FULL backups.

Our databases are over 1TB and the guideline is 1-2% of db main space ( 10-20GB per 1TB) to be allocated to IQ SYSTEM main.

We tend to increase our total allocation of dbmain  4 TB every quarter so it is not realistic to keep SYS MAIN @ the recommended levels.

On our server we had the issue on we were at 240 GB for years for SYS MAIN and the database has grown to 37 TB of 45TB used.

Adding 300 GB to increase SYS MAIN to 540 GB fixed the problem.

Is the calculation of recommended system main based on total allocation 45TB or the usage 37 Tb?

Being that we’ve not had to increase our SYS MAIN in years and only seeing this issue now leads me to believe we don’t have to keep up on the space recommendation.


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