Database Parameters

Definition

The SAP System for the Oracle database comes with a standard initialization profile for the database parameters:

·        UNIX

OS> <ORACLE_HOME>/dbs/init<DBSID>.ora

·        Windows

OS> <ORACLE_HOME>\database\init<DBSID>.ora

For example (UNIX):

/oracle/C11/dbs/initC11.ora

Use

This profile contains the default parameter settings recommended for the SAP System. Copy this standard profile so that you can access the original parameters, if necessary.

Structure

Operating System-Specific Parameters

All parameters that specify paths and file names are operating system-specific. These parameters have to be adjusted to agree with your operating system. When possible, however, SAP recommends that you retain the default path and file descriptions in the system. Make the appropriate changes to your operating system instead.

?is the Oracle placeholder for $ORACLE_HOME.

Parameter

SAP recommendation

control_files

See Mirroring the Control File.

log_archive_dest

OS> ?/oraarch/<DBSID>arch, where ?/oraarch can be a soft link to a separate disk or a separate mount point.
See Setting Up Archiving.

background_dump_dest

OS> ?/saptrace/background Directory for database trace and database ALERT files.

If you have serious database problems, you must analyze the information in the ALERT and trace files.

user_dump_dest

OS> ?/saptrace/usertrace Directory for user trace files.

Tuning Parameters

The following lists a selection of RAM-dependent tuning parameters. For more information, see the Oracle documentation.

Parameter

Settings

ram (unit: MB)

Portion of physical RAM that you want to reserve for the system.

One system installed on one host:

ram = 1.0*RAM

Two systems installed on one host:

ram = 0.5*RAM

rating

Proportion of RAM taken up by the database and the SAP System

Default: rating=0.25 (25% of RAM reserved for the database, 75% for the SAP System)

Database-only server: rating=0.8 (80% of RAM is reserved for the database)

If ram<RAM*0.8: rating=1.0 (100% of RAM is reserved for the database)

db_block_size

db_block_size
(unit: bytes) size of the Oracle database blocks

Operating system-specific, default: 8192

The parameters ram, ratingand db_block_size are taken into account when calculating the following tuning parameters:

Parameter

Determination of its value

shared_pool_size

db_block_size
(unit: bytes) buffer size for parsed SQL statements in the Oracle System Global Area (SGA)

shared_pool_size=ram*rating*0.4*1024*1024

The factor 0.4 means that shared_pool_size occupies 40% of the calculated SGA.
shared_pool_size=20.971.520 if the value calculated using the formula above is lower than 20971520 Bytes.

db_block_buffers

db_block_size
(unit: blocks) buffer size for data blocks and index blocks in the Oracle SGA

db_block_buffers=ram*rating*0.6*1024*1024/db_block_size

The factor 0.6 means that db_block_buffers occupies 60% of the calculated SGA.

log_buffer

db_block_size
(unit: bytes) buffer size for redo log entries in the Oracle SGA

Default: log_buffer=327.680

Part of the SGA, which is very small when compared with shared_pool_size and db_block_buffers.

row_cache_cursors

Number of cursors used for selecting lines from the data dictionary.

row_cache_cursors=

300, if ram>=256

200, if ram<256

100, if ram<128