ASMCMD cp command fails with ORA-15046

Symptoms

ASMCMD cp command fails with

ORA-15046: ASM file name +DGEXTBK/prod/datafile/tbsext.256.628847401' is not in single-file creation form

Cause

The target file name specified is not a valid file name.
The cp command failed because the ASM file name was not in a form that can be used to create an single file.
The file name should not contain the file number/incarnation.

Example 1
==========
ASMCMD> cp +DGEXT/orcl/datafile/tbsext.256.628847401 +DGEXTBK/prod/datafile/tbsext.256.628847401

source +DGEXT/orcl/datafile/tbsext.256.628847401
target +DGEXTBK/prod/datafile/tbsext.256.628847401
ASMCMD-08015: can not create file->'+DGEXTBK/prod/datafile/tbsext.256.628847401'
ORA-15056: additional error message
ORA-17502: ksfdcre:4 Failed to create file +DGEXTBK/prod/datafile/tbsext.256.628847401
ORA-15046: ASM file name '+DGEXTBK/prod/datafile/tbsext.256.628847401' is not in single-file creation form
ORA-06512: at "SYS.X$DBMS_DISKGROUP", line 142
ORA-06512: at line 3 (DBD ERROR: OCIStmtExecute)
ASMCMD-08016: copy source->'+DGEXT/orcl/datafile/tbsext.256.628847401' and target->'+DGEXTBK/prod/datafile/tbsext.256.628847401' failed 

Example 2
==========
ASMCMD> cp +DGEXT/orcl/datafile/tbsext.256.628847401 +DGEXTBK/prod/datafile/tbsext.257.628847401

source +DGEXT/orcl/datafile/tbsext.256.628847401
target +DGEXTBK/prod/datafile/tbsext.257.628847401
ASMCMD-08015: can not create file->'+DGEXTBK/prod/datafile/tbsext.257.628847401'
ORA-15056: additional error message
ORA-17502: ksfdcre:4 Failed to create file +DGEXTBK/prod/datafile/tbsext.257.628847401
ORA-15046: ASM file name '+DGEXTBK/prod/datafile/tbsext.257.628847401' is not in single-file creation form
ORA-06512: at "SYS.X$DBMS_DISKGROUP", line 142
ORA-06512: at line 3 (DBD ERROR: OCIStmtExecute)
ASMCMD-08016: copy source->'+DGEXT/orcl/datafile/tbsext.256.628847401' and target->'+DGEXTBK/prod/datafile/tbsext.257.628847401' failed

Solution

The cp command failed because the ASM file name was not in a form that can be used to create an single file.File name should not contain the file number/incarnation

ASMCMD> cp +DGEXT/orcl/datafile/tbsext.256.628847401 +DGEXTBK/prod/datafile/tbsext
source +DGEXT/orcl/datafile/tbsext.256.628847401
target +DGEXTBK/prod/datafile/tbsext
copying file(s)...file, +DGEXTBK/prod/datafile/tbsext, copy committed.