Space Management with MaxDB

Purpose

Poor space management can lead to downtime because the database instance runs out of space. It is far better to prevent this problem than to recover from it. You can use the Database Manager to manage space in the MaxDB database instance.

Prerequisites

In the following scenarios, a MaxDB database instance stops processing, so that SAP applications can no longer continue:

·        Database usage level 100%

This means there is no more space in the data area of the database instance. You must quickly provide more space by adding a new data volume to the database instance. You can normally add a new data volume in ONLINE state using the Database Manager.

·        Log usage level 100%

During normal database operations (that is, in ONLINE state), you can back up the log area without affecting SAP applications. If you do not back up the log area, messages are sent to the knldiag file and to the alert monitor in the SAP system. If the error message for a full log area appears, SAP applications cannot continue until you have backed up the log area.

To avoid the log area filling up, use the automatic log backup. To do this, use CCMS function Activating Automatic Log Backups to activate the automatic log backup or use the corresponding Database Manager function. This means that, as soon as a log segment is full, it is backed up to the specified version file.

Process Flow

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       1.      You regularly monitor the database instance and log usage levels.

The recommended way to manage space on your database instance is using the CCMS or Database Manager. For routine monitoring, use the alert monitor in the CCMS. The CCMS and Database Manager present information in different ways and you should familiarize yourself with both to obtain the best possible picture of the state of database objects.

       2.      You install your database instance optimally for production.

Optimal installation of your database instance in view of the disks available and anticipated requirements can prevent future problems. This means correctly sizing the database instance (for example, size and number of data volumes) when you set the database parameters.

       3.      You monitor the database instance usage level.

You need to closely watch the expansion of the data in the database instance. Use the CCMS or Database Manager to monitor the fill level.

       4.      If required, you add a data volume.

As the result of your monitoring, you might decide to add a new volume to the database instance. Use the Database Manager to do this before the situation becomes critical.

First, check whether the database parameter MAXDATAVOLUMES is large enough to add a new volume. If this parameter is large enough, you can add the volume in ONLINE state. Otherwise, you have to increase the General Database Parameter MAXDATAVOLUMES, then stop and start the database instance, before you can add a new data volume.

       5.      You monitor the log usage level.

You can observe the log usage level with the CCMS or Database Manager. Make sure the log usage level does not approach 100%. Once you have backed up the log area, it is automatically free for re-use.

       6.      You backup log segments.

Configure the log segment size as follows using the Database Manager:

0 <= <log_segment_size> <= <50_%_of_the_whole_log_area>

If you do not configure the log segment size, the default value is a third of the whole log area. If you configure a value higher than 50 %, the default value is 50 % of the whole log area.

You can back up log segments automatically. To do this, enable the automatic log backup using the CCMS or Database Manager. As soon as a log segment is full, the database backs up that log segment and releases it for further use.

See also:

Concepts of the Database System,

·        Administration

·        Monitoring