Oracle Database Discussions

I list most of possible background processes that should exist in a healthy database instance.

For example,
when each individual background process is down and need to re-start it, how do I have to do to bring then up?

ora_arc0_<SID>
ora_arc1_<SID>
ora_smon_<SID>
ora_ckpt_<SID>
ora_snp0_<SID>
ora_reco_<SID>
ora_snp1_<SID>
ora_lgwr_<SID>
ora_dbw0_<SID>
ora_pmon_<SID>

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assume, ONLY archive log engine is down and the rest of background processes are still running,
to bring up archive process, you can do,
SQL> archive log start;

For the same situation, what do I do to bring each one up?

ora_smon_<SID>
ora_ckpt_<SID>
ora_snp0_<SID>
ora_reco_<SID>
ora_snp1_<SID>
ora_lgwr_<SID>
ora_dbw0_<SID>
ora_pmon_<SID>


thanks in advance!