Instead of, or in addition to, listing specific file names, you can use the DUMPFILE parameter during export operations to specify multiple dump files, by using a substitution variable (%U) in the file name. This is called a dump file template. The new dump files are created as they are needed, beginning with 01 for %U, then using 02, 03, and so on. Enough dump files are created to allow all processes specified by the current setting of the PARALLEL parameter to be active. If one of the dump files becomes full because its size has reached the maximum size specified by the FILESIZE parameter, then it is closed and a new dump file (with a new generated name) is created to take its place.
If multiple dump file templates are provided, they are used to generate dump files in a round-robin fashion. For example, if expa%U, expb%U, and expc%U were all specified for a job having a parallelism of 6, then the initial dump files created would be expa01.dmp, expb01.dmp, expc01.dmp, expa02.dmp, expb02.dmp, and expc02.dmp.
For import and SQLFILE operations, if dump file specifications expa%U, expb%U, and expc%U are specified, then the operation begins by attempting to open the dump files expa01.dmp, expb01.dmp, and expc01.dmp. It is possible for the master table to span multiple dump files, so until all pieces of the master table are found, dump files continue to be opened by incrementing the substitution variable and looking up the new file names (for example, expa02.dmp, expb02.dmp, and expc02.dmp). If a dump file does not exist, then the operation stops incrementing the substitution variable for the dump file specification that was in error. For example, if expb01.dmp and expb02.dmp are found but expb03.dmp is not found, then no more files are searched for using the expb%U specification. Once the entire master table is found, it is used to determine whether all dump files in the dump file set have been located.