%t %u %g meaning in Oracle Managed Files

File Type       Format           Example
     ---------       ------           -------
     Datafile        ora_%t_%u.dbf    ora_tbs1_6xzas83w.dbf
     Tempfile        ora_%t_%u.tmp    ora_temp1_7d4g46af.tmp
     Redo log file   ora_%g_%u.log    ora_1_yr3566xq.log
     Control file    ora_%u.ctl       ora_xs43q25e.ctl

  Meaning:
     %t is the tablespace name (possibly truncated)
     %u is an eight character string that guarantees uniqueness
     %g is the online redo log file group number