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Plan the most important database properties before you create a database. The following questions are particularly significant:

  • How much application data do you expect (database size)?

  • What are your security requirements (hardware selection, system landscape)?

Procedure

Database Size

When creating the database, you create data volumes for storing application data and log volumes for storing the log entries. The database size is mainly determined by the size of the data area (set of all data volumes).

More information: Concepts of the Database Systems, How Databases Store Data and Log Entries

Note Note

You can add or delete volumes later.

End of the note.

The maximum number of data volumes is controlled by the MaxDataVolumes general database parameter. More information: General Database Parameters

The larger you choose the value for the ConverterVolumeIdLayout special database parameter, the more data volumes you can use. The maximum permitted size of the individual data volumes is reduced accordingly. More information: Special Database Parameters

Restrictions for Volumes

Description

Calculation Formula

Minimum Value

Maximum Value

Number of data volumes

2^(ConverterVolumeIdLayout)-1

1

4095

Note Note

The default value of ConverterVolumeIdLayout is 8.

With this default value, the maximum number of data volumes is 255.

End of the note.

Size of a data volume

<page_size>x(2^(32-ConverterVolumeIdLayout)-1)

Page size = 8 KB

1000 pages or 8000 KB

512 GB

Note Note

The default value of ConverterVolumeIdLayout is 8.

With this default value, the maximum size of a data volume is 128 GB.

End of the note.

Size of the data area (sum of all data volumes)

-

1000 pages or 8000 KB

32 TB

Number of log volumes

-

1

10,000

Size of a log volume

-

-

32 TB

Size of the log area (sum of all log volumes)

-

-

32 TB

Recommendation Recommendation

If you create data volumes of the FILE type in SAP systems, use the following calculation formula: Calculate the square root of the total amount of space in GB available for data volumes and round up to the nearest integer.

Example: Up to 50 GB of space is available for data volumes. Square root (50) = 7.07, which means that 8 data volumes are recommended.

End of the recommendation.
Hardware Selection

The speed with which the database system can read data from the volumes and write data to the volumes has a significant influence on the performance of the database.

As the database system logs all data changes in the log volumes, the log volumes are the areas of the database with the highest write activity.

  • Use different hard disks for data volumes and for log volumes.

    More information: SAP Note 869267 (FAQ: MaxDB LOG area)

  • Do not use hard disks on which swap and paging areas can be found for log volumes.

  • If you are using several disks for the volumes, use disks with standardized performance specifications, in particular standardized access speeds. This is the only way to ensure that the disks are filled evenly.

  • Unix and Linux only: Do not use a hard disk with a journal file system for the volumes. Journal file systems perform their own logging of data changes, which is unnecessary for the database system and leads to performance reduction.

  • If your operating system supports the switching off of its own buffer cache, configure the support database parameters UseFilesystemCachingForVolume and UseFilesystemCachingForBackup accordingly.

    More information: Support Database Parameters

RAID Systems

  • Mirror the log area using hardware-based means, for example by using RAID-1, RAID-10, RAID-0+1or RAID-DP systems. We recommend not to use RAID-5 systems (for security and performance reasons). When you select your RAID system, make sure that the RAID controller has a good write performance and that caches can still be backed up to disk even when there is a power outage.

    If hardware-based mirroring of the log area is not possible, then configure the database log mode so that the database system mirrors the log area.

  • Even if you are using RAID systems for your data area, create several data volumes for the database. Because some of the database system’s parallelization techniques depend on the number of data volumes, you can improve performance if you use several data volumes instead of one data volume.

  • If you are using fault-tolerant hardware, then expand the capacity only using the same type of hardware. For example, expand RAID-5 systems with RAID-5 systems only.

Raw Devices

  • On Unix systems, you can use raw devices for data and log volumes. In general the database can access raw devices quicker than files. The operating system can also start raw devices more quickly because it does not need to check the consistency of the file system.

  • Do not configure raw device type data volumes larger than the actual size of the raw device.

  • Make sure that only one database accesses one raw device.

More information: SAP Note 912905 (FAQ: Storage systems used with MaxDB)

Processor Architecture

We recommend that you run SAP MaxDB on a 64 bit platform. The SAP MaxDB architecture benefits greatly from the advantages of 64 bit platforms (for example, better memory management).

More information: SAP Note 1013441 (Upgrade required: Advantages for MaxDB on 64-bit platforms)

More Information