interview question perhaphs :-)
Hi
I am a OCP DBA :-) and i do not know the answers to this questions..all of you are welcome to cricize me :-) for askin this simple question..but i have serached the docs before askin this ?
here goes my 2 questions
1)when is the SCN assigned to a transaction..immediately after a commit is issued or after the contents of the redolog buffer are flushed to the disk
2)when you have row migration why does oracle keep a pointer in the block to the row where it has moved now ?
regards
Hrishy
Re: interview question perhaphs :-)
Quote:
Originally posted by hrishy
1)when is the SCN assigned to a transaction..immediately after a commit is issued or after the contents of the redolog buffer are flushed to the disk
Whenever a transaction is committed, LGWR writes the transaction’s redo records from the redo log buffer of the SGA to an online redo log file, and a system change number (SCN) is assigned to identify the redo records for each committed transaction.
Quote:
Originally posted by hrishy
2)when you have row migration why does oracle keep a pointer in the block to the row where it has moved now ?
Only reason i think is to preserve the rowid. The rowid never changes for a row :)
HTH
Re: Re: interview question perhaphs :-)
Quote:
Originally posted by adewri
Only reason i think is to preserve the rowid. The rowid never changes for a row :)
HTH
Hi Amar.
Dude thats a cool answer...even i couldnt think of any other answer..
regards
Hrishy
Re: interview question perhaphs :-)
Quote:
Originally posted by hrishy
Hi
2)when you have row migration why does oracle keep a pointer in the block to the row where it has moved now ?
regards
Hrishy
It's especially essential if the row is in a table that is a Master table for a materilized view (using ROWID), otherwise, every time you had a row migration, you'd have to rebuild the materialized view.
Just one example... :)
Don't worry about asking questions, even DBA's with 10+ years experince don't know everything. If they did.. it'd be a pretty boring job.
Re: Re: interview question perhaphs :-)
Quote:
Originally posted by adewri
Only reason i think is to preserve the rowid. The rowid never changes for a row
Presumably if the rowid did change, all the indexes pointing to it would have to be updated too.