Re: database buffer cache / SGA

In article <3B577825.1BB18144_at_att.net>, stevek says...
>
>Oracle server receives a request from a client, run sql through sqlarea
>in cache, if there runs,if not runs through plan process then executes,
>if data in buffer cache uses that data otherwise get block(s) from
>tablespace.
>
>Question: oracle deals with data in blocks only, block 8K, record 1K.
>Does oracle take 7 additional records on the block read? Does it use the
>same block size/number of records when it puts changed data in redo logs
>and rbs?

data is cached in blocks, you get the block cached, even if you want just 1 of the rows on that block.

redo -- changed bytes (not even entire rows), unless the tablespace is in HOT backup mode then the first time a block is modified the entire block is written to redo and then changed bytes only after that.

rollback -- changed bytes only.

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