To delete a column from a MySQL table run the following command:
Prevent Changes to System Properties in Tenant Databases
To ensure the stability and performance of the overall system or for security reasons, you can prevent certain system properties from being changed by tenant database administrators, for example, properties related to resource management. A configuration change blacklist is available for this purpose. You configure the blacklist in the SAP HANA cockpit.
How to set allocation limit for tenant databases
You want to manage and control the memory usage of your multiple-container system by configuring global allocation limit for individual tenant databases.
SAP Hana: Reset the SYSTEM user password
Resetting the SYSTEM User's Password in the admin guide for SP7 discusses how to do this: http://help.sap.com/hhxe/SAP_HHXE_Administration_Guide_en.pdf