Managing Serviceguard Extension for SAP Version B.05.10, December 2012

shown that it is a good practice to create local copies for all files in the central executable directory.
This includes shared libraries delivered by SAP.
To automatically synchronize local copies of the executables, SAP components deliver the sapcpe
mechanism. With every startup of the instance, sapcpe matches new executables stored centrally
with those stored locally.
Directories that Reside on Shared Disks
Volume groups on SAN shared storage are configured as part of the SGeSAP packages. The
volume groups can be following:
• Instance specific
• System specific
• Environment specific
Instance-specific volume groups are required by only one SAP instance or one database instance.
They usually get included with exactly the package that is set up for this instance.
System-specific volume groups get accessed from all instances that belong to a particular SAP
System. Environment-specific volume groups get accessed from all instances that belong to all SAP
Systems installed in the whole SAP environment. System and environment-specific volume groups
are set up using HA NFS to provide access for all instances. They shouldn't be part of a package
that is only dedicated to a single SAP instance if there are several of them. If this package is down,
then other instances would also be impacted. As a rule of thumb, it is a good default to put all
these volume groups into a package that holds the database of the system. These filesystems often
provide tools for database handling that don't require the SAP instance at all.
In consolidated environments with more than one SAP application component, the recommendation
is to separate the environment-specific volume groups to a dedicated HA NFS package. This
package will be referred to as sapnfs package. It should remain running all the time, since it is
of central importance for the whole setup. Because sapnfs is serving networked file systems, there
rarely is a need to stop this package at any time. If environment-specific volume groups become
part of a database package, there is a potential dependency between packages of different SAP
Systems. Stopping one SAP System by halting all related Serviceguard packages will lead to a
lack of necessary NFS resources for unrelated SAP Systems. The sapnfs package avoids this
unpleasant dependency. It is an option to also move the system-specific volume groups to the
sapnfs package. This can be done to keep HA NFS mechanisms completely separate.
A valuable naming convention for most of these shared volume groups is vg<INSTNAME><SID>
or vg<INSTNAME><SID><INR>. Table 4 (page 32)and Table 5 (page 33) provide an overview
of SAP shared storage and maps them to the component and package type for which they occur.
Table 4 Instance Specific Volume Groups for exclusive activation with a package
Device minor
number
VG NameRecommended packagesAccess PointMount Point
jci<SID>
(scs<SID>)
Shared disk/usr/sap/<SID>/SCS<INR>
jdbjci<SID>
ci<SID>
(ascs<SID>)
/usr/sap/<SID>/ASCS<INR>
dbci<SID>
ers<INR><SID>/usr/sap/<SID>/ERS<INR>
ci<SID>/usr/sap/<SID>/DVEBMGS<INR>
dbci<SID>
d<INR><SID>
32 Planning the Storage Layout