ORACLE Databases and Parallel Server Option: Overview

The ORACLE Parallel Server option (OPS) is described in the corresponding ORACLE documentation. Only the most important features of the OPS configuration when using the SAP utility programs will be discussed here:

• All control files, online redo log files and database data files are on raw devices, which can be accessed from all hosts in a cluster (the raw devices are shared).
• On the hosts in the cluster, there are several ORACLE instances, which can access the database files (normally one instance per host).
• Every ORACLE instance has a unique name (this is a SAP standard) - the so-called ORACLE system ID. When setting up a connection to the database, the ORACLE instance is determined by the environment variable ORACLE_SID (abbreviated, DBSID) or by a connect string.
• Every ORACLE instance uses separate online redo log groups which can also contain mirrored online redo log files. All groups in one instance set up a so-called online redo thread which is identified by a number.
• Every ORACLE instance writes separate offline redo log files which are identified by the thread number and the sequential log sequence number. The offline redo log files are stored in a file system as normal files. You can normally only access this file system locally, that is, from the host on which the instance runs.
• Every ORACLE instance has a separate profile init.ora which, among other things, determines the thread number (parameter thread), the archiving directory (parameter
log_archive_dest) and the name format of the offline redo log files (parameter log_archive_format). See Archiving Parameters The corresponding character strings can contain the usual placeholders ? () and @ (). To avoid problems, this is only allowed in the following form:

– log_archive_dest = ?/saparch/arch

In the standard installation, all the instances should have the same . If they have different values, the question mark must be replaced directly: log_archive_dest = /oracle//saparch/arch

– log_archive_format = %t_%s.dbf

• One of the ORACLE instances (for SAP installations normally the instance with thread number 1) is the so-called dedicated database instance (DDB instance). All administration tasks in the database (for example database backup, tablespace extension, reorganization) are carried out from this instance.
• The standard assignment instance (ORACLE_SID or DBSID) and thread look like this in an R/3 System C11 (also compare with the above graphic):

Instance (DBSID)	Thread
C11	1 (DDB instance)
C11_002	2
C11_003	3
...	...

Before you work with your OPS database, you must become familiar with the concrete installation. Use all the available information, such as the installation guidelines.

• You must be able to administrate all ORACLE instances from the DDB instance, that is, you must be able to start and stop them from the DDB instance. You must be able to perform these operations from a local SVRMGR session. In order to do this, the following requirements must be met:

– Create an ORACLE password file:

orapwd file= /dbs/orapw
password= entries=100

Create softlinks to this file for all other database instances:

cd /dbs
ln -s orapw orapw

– The parameter remote_login_passwordfile = exclusive must be entered in all the init.ora profiles or in a common Include file (which is then linked into all the profiles with the IFILE parameter). If the parameter was only entered after an instance(s) was started, the corresponding instances should be started so that it takes effect.

– User system must have SYSOPER authorization on the DDB instance. To do this, start SVRMGR as user internal and execute the following ORACLE command:

svrmgr> grant sysoper to system ;

– It might be necessary to change the password for user system:

svrmgr> alter user system identified by ;