Increasing SVC Dump space after IEA043I or IEA611I

Products

Datacom Datacom/AD Datacom/DB

Issue/Introduction

When trying to take an SVC dump (SDUMP), if you do not have enough space for the dump areas, you could receive one or both of these messages:

IEA043I SVC DUMP REACHED MAXSPACE LIMIT - MAXSPACE=xxxxxxxx MEG
IEA611I {COMPLETE|PARTIAL} DUMP ON dsname. MAXSPACE LIMIT REACHED WHILE CAPTURING DUMP

How can I determine what my settings are and how do I increase my space?

Environment

Release : All

Component : Datacom/AD

Component : Datacom/DB

Component : All

Resolution

If you have received one of the messages shown above, you need to look at your system to determine your current settings, and what you need to do before increasing the maximum space used for SVC dumps. Bear in mind that the objective is to not cause an outage due to creating a dump, and to capture the diagnostic data quickly enough without causing much of a performance disruption.

This information is extracted from SHARE Anaheim 2014, Session 14254, with the title, "Common z/OS Problems You Can Avoid."

The MAXSPACE parameter acts as a throttle to limit the maximum amount of virtual storage that SDUMP can “capture” at any given time.

Storage can belong to one or more captured SDUMPs
MAXSPACE is set via the CHNGDUMP (CD) command
To change it, CD SET,SDUMP,MAXSPACE=yyyyyyyyMeg (default = 500M, can range from 1-99999999)

Here are some steps to help you set MAXSPACE:

Check the sizes of your largest dumps. Given these sizes, what seems like a reasonable value for MAXSPACE?
Examine your AUX storage definitions. How much is 1/3rd of your AUX?
If Answer1 <= Answer2, then choose a MAXSPACE value between the two. This will protect your system while giving you the greatest probability of obtaining a complete dump.
If Answer1 > Answer2, then you need to make a decision:
- To minimize the likelihood of a partial dump, increase your AUX storage definition to at least 3 times the MAXSPACE that you require.
- If you are not in a position to increase your aux storage definition, then you will need to lower MAXSPACE to 1/3rd of the defined size.

Keep these things in mind as you consider your dump management practices:

Partial dumps compromise the ability to diagnose critical problems
SDUMP tries to dump storage strategically by starting with the more critical areas of storage

There are several other factors involved in dump creation successes or failures. For example, even with a properly set MAXSPACE, SDUMP can still trigger an AUX storage condition if the overall system is using a sizeable amount of AUX storage. The AUXMGMT parameter offers additional system protection and acts as a safety net for systems exceeding recommended AUX utilization (=30%). With this parameter, SDUMPs are prevented or stopped when AUX storage is not sufficient.

If set correctly, MAXSPACE and AUXMGMT work hand in hand to protect the system and allow you to create the dumps needed to diagnose your problems.

Additional Information

For more information on dump processing and the different dump options available, please refer to Knowledge Base article 30191, titled "IBM MVS dump options for a complete dump."

Although it is a little dated, another good reference is the IBM Redbook, "z/OS Diagnostic Data Collection and Analysis."

For setting the dump parameters, please see IBM documentation for the z/OS CHNGDUMP command: "Setting the dump modes and options."