/usr/lib/acct/acctmerg [-a] [-i] [-p] [-t] [-u] [-v] [filename] ...
acctmerg reads its standard input and up to nine additional files, all in the tacct format (see acct.h(3HEAD)) or an ASCII version thereof. It merges these inputs by adding records whose keys (normally user ID and name) are identical, and expects the inputs to be sorted on those keys.
The following sequence is useful for making "repairs" to any file kept in this format:
example% acctmerg -v <filename1>filename2
Edit filename2 as you want:
example% acctmerg -i <filename2>filename1
|February 22, 1999||OmniOS|