Data received for the EG data stream identified by EG stream are associated with all tape streams identified by the following lists of client identifiers.
Each list of client identifiers receives a copy of the data for this EG data stream (data duplication). The data is then written in a round robin manner to each of the tape devices implied by the client identifiers in the list (data striping).
A null request may be used to cancel any existing association.
The current state of the EGTS must be halted otherwise the request will fail.

This procedure defines the way incoming experimental event-by-event data should be distributed to the available real data device streams. The online event formatting system allows events to be written to up to 4 event streams. The Associate Data Stream procedure is used to route each data stream to one or more lists of device streams.
The associate mode = 2 (modes 0 and 1 were used by earlier versions of the program protocol and are now obselete). Mode 2 allows one or more lists of device identifiers; each list may contain one or more device identifiers.
Each list of client identifiers receives a copy of the incoming data for this Data Stream. This enables online duplication of the experimental data and will generate a number of identical copies of the original raw data. Not only does this give greater security to the original data but is more efficient than offline duplication of the data tapes. Each of these lists may itself be a list of device identifiers. The data is written in a round robin manner to each of the devices implied by the client identifiers in the list. This enables experimental data to be handled at data rates which are several times the data rate possible for an individual data device. By using round robin scheduling all data devices in a list receive data at the same rate and hence at any time have approximately the same amount of data written to them and all devices in a list will reach end of tape at about the same time. Additionally ,if necessary, since the data blocks have been written to the members of the list in a defined and predicably manner it is possible easily to read the tapes and recover the original data ordering.
Association to a null list cancels any existing association. An Associate Stream procedure overwrites any existing association. This procedure is only valid if the Tape Server is in the Halted state.