SAP recommends that you use the C-shell (csh) because then the fewest problems occur within the SAP software.
As an alternative, you can use the Bourne shell (sh), which is also supported by SAP. Since the Bourne shell does not support the alias command, the aliases for startsap and stopsap are not defined when you use the Bourne shell as a login shell. For this reason, the SAP system must be started and stopped by calling up the corresponding scripts.
In general, you can use the Korn shell (ksh) as a login shell, however, note that the implementation of the Korn shell differs among the different UNIX platforms. This has lead to problems within SAP, in particular this is the case when you start external programs from an SAP system.
In principle, you can use the tcsh shell as a login shell. Note, however, that the implementation of the tcsh differs among the various UNIX platforms.
Nevertheless, if you use the ksh or tcsh as a login shell for the user <sid>adm or the database administrator, first consider using the csh or sh shell if problems occur while using the SAP software. These problems would involve calling a ksh or a tcsh shell, either directly or indirectly.
By default, the C shell is assigned as a login shell to all users created during the installation of an SAP system. You can change the login shell of a user with the administration tools of the respective operating system later.