SAP OS Level Directory Structure

Main directory

/usr/sap  - physical parent directory
/usr/sap/trans  - transport directory
/usr/sap/SID  - SAP system parent directory
/usr/sap/SID/SYS  - contain common & global SAP system files(i.e. profile, global, and exe directory)
/usr/sap/SID/<instance_name>  - contain SAP instance specific directories(i.e. data, log, and work)
/sapmnt  - directory structure for sharing common files to all system belonging into the same group
/sapmnt/SID  - link or share folder of directory /usr/sap/<SID>/SYS
/oracle  - directory of the whole database system
/oracle/stage  - directory that used for database installation and upgrades
/oracle/SID  - directory of the whole database application and data files

Shared directory:
/sapmnt/SID/profile  - SAP instance profile
/sapmnt/SID/global  - SAP central system log
/sapmnt/SID/exe  - SAP executable application directory
Transport directory:
/usr/sap/trans  - main transport directory
/usr/sap/trans/bin  - contain TPPARAM file (global transport parameter)
/usr/sap/trans/data  - contain transport data file
/usr/sap/trans/log  - transport logs, trace and statistic file
/usr/sap/trans/buffer  - special buffer with the SID of every system in the transport group (including control information)
/usr/sap/trans/cofiles  - control file directory
/usr/sap/trans/sapnames  - contain information of SAP User that performs export and keep tracks of each transport status
/usr/sap/trans/tmp  - temporary directory
/usr/sap/trans/actlog  - action log files (managed by SAP system)
/usr/sap/trans/olddata  - archived transport files
/usr/sap/trans/backup  - directory of logical backup with R3trans program
/usr/sap/trans/serial  - contain serialization of tp