ERROR: alter system dump datafile/tempfile: invalid input file

Troubleshooting the "buffer busy wait" event with parameters 
p1=212
p2=2
p3=13

i decided to dump the block #2 in database file # 212.
The simple command:

alter system dump datafile 212 block 2;

generated the error message in trace file:

ERROR: alter system dump datafile/tempfile: invalid input file # 212

Should i use TEMPfile keywork? And the 2nd run
alter system dump tempfile 212 block 2;
brought the same error message to the trace file :(((.

The working syntax: use the file name (not a number)

alter system dump tempfile '+DATA/STAGESTB/TEMPFILE/TMP03.1566.1191597171'  block 2;

The syntax:

ALTER SYSTEM DUMP { DATAFILE | TEMPFILE } { file_num | 'file_name' } { BLOCK block_num | [ BLOCK MIN block_num ] BLOCK MAX block_num } ;