Specifications

SAP R/3 Sizing and Installation Planning 147
5.4 Installation Planning of Database for the SAP R/3 System
This section is divided into three subsections on the basis of the database being
used (for example, DB2, Oracle and MS SQL Server).
5.4.1 DB2 Database Server Installation Planning
5.4.1.1 Distribution
1. Distribute database files(<DRIVE>:\db2\<SAPSID>\sapdata<N>) and archive
log files(<DRIVE>:\db2\<SAPSID>\SQLOGDIR) to different disks.
2. The archive log files should be located on the disk with low I/O. Avoid, for
example, accommodating the logs on the same disk as the operating system’s
paging files or on disks with transaction data.
5.4.1.2 Distribution of SAP Software using RAID
For safety and performance reasons it is essential that a minimum of three logical
disk volumes are used to separate the active database log files, archived log files
and database files.
The active database log files(\db2\<SAPSID>\SQLOGDIR) must reside on a
logical volume using RAID 1(Disk Mirroring). They must be separated from the
archived log files(\db2\<SAPSID>\log_archive) which can optionally reside on a
RAID 1 disk volume. The mirroring is recommended because of safety for
production systems.
The data files(\db2\<SAPSID>\sapdata1 ... \db2\<SAPSID>\sapdata<N>) should
be located on a logical disk volume using RAID 5(distributed parity checking).
5.4.1.3 Distributing SAP using Separate Disks
For safety reasons always distribute the following directories to separate physical
disks:
• The database log files(\db2\<SAPSID>\SQLOGDIR)
• The mirrored database log files(by NT disk mirroring)
• The archived log files(\db2\<SAPSID>\log_archive)
• All DB2 common server data file directories (sapdata1 - sapdata<N>)
For performance and security reasons, archived log files and active
log files must reside on separate physical disks. As DB2 writes the
log records of a transaction synchronously to disk as soon as the
transaction has been committed. Therefore, you should use the
fastest disk of your system for database logging.
Note
To distribute the directories in this way, you need a minimum of five
disks. The remaining directories can be distributed to any of these
five disks.
Note