Abstract: A file based and highly available hybrid database using resident databases (16, 17, 18) on data control computer systems (31, 32, 33) which are linked together as part of a computer network (29). Resident databases (16, 17, 18) are selected to store master file groups (19,21,22,23) the information being copied to other resident databases (16, 17, 18). All database transactions are controlled by interacting client (11) and server (12, 13, 14) processes using the computer network (29) to copy a master file group (19, 21, 22, 23) to the client system for use and then restores the master file group (19, 21, 22, 23) to the appropriate master database (16, 17, 18).

Abstract: An elongate mercaptan injection apparatus is disclosed. From the remote end, there is an external fitting for connection with a supply line of liquid mercaptan. It communicates serially with an internal check valve captured in a chamber. The check valve includes a spring and ball cooperative with a valve seat. Through the check valve, the liquid mercaptan flows into an elongate hollow tubular member which is sealed externally with a number of fittings to prevent leakage. It extends to the interior of the pipeline through a fitting which seals to the wall of the pipeline. On the interior, it connects with an elongate hollow member packed with particulate material. A number of transverse openings provide cross ventilation so that flowing natural gas is able to pass through the particulate material.