Confused with oracle username

[A K]

I am a naive at oracle , my first request is can any body tell me whether or not an oracle user name can consisting only of integers.

[debasisdas]

No

That is not possible. Oracle does not support that.
Even an user name can't start with number same rule for password also.

[gintsp]

I am a naive at oracle , my first request is can any body tell me whether or not an oracle user name can consisting only of integers.

See database object (identifier) naming rules here

And BTW DON'T use qouted identifiers without VER VERY strong necessity.

Excerpt:

Nonquoted identifiers must begin with an alphabetic character from your database character set. Quoted identifiers can begin with any character.

Nonquoted identifiers can contain only alphanumeric characters from your database character set and the underscore (_), dollar sign ($), and pound sign (#). Database links can also contain periods (.) and "at" signs (@). Oracle strongly discourages you from using $ and # in nonquoted identifiers.

Quoted identifiers can contain any characters and punctuations marks as well as spaces. However, neither quoted nor nonquoted identifiers can contain double quotation marks or the null character (\0).

Gints Plivna
http://www.gplivna.eu