The event recorder

The event builder is the event producer for the DD/ET buffer manager. The CODA framework provides a standard event consumer, the event recorder. The event recorder takes events out of the buffer manager and writes them to disk. The writing is done by a user defined file format library containing routines for opening, closing and writing to data files. It is common in CODA systems at Jefferson Lab to write data to disk then copy the files to tape. Direct tape writing could be implemented by modifying the file format library and replacing the calls to evOpen, evClose and evWrite with the appropriate calls to manage a tape drive. The default library writes CODA or binary format files to disk. The CLAS collaboration has developed a plug-in library to write FPACK files. The event recorder can split the data files on user defined boundaries, i.e. every 2GB. It can also run an optional Tcl script to calculate the data file name. For example the script could read the free space left on a disk and generate a file name pointing to a new empty disk. This script could also be used to automatically start the transfer from disk to tape.