Visit http://www.ixora.com.au where much info about the (really relevant) x$
views can be found.
Marcel Kraupp <marcel.kraupp_at_gmx.ch> schreef in berichtnieuws
332bb004.0205272053.1e7f177a_at_posting.google.com...
| Hello
|
| I am trying to get into deeper knowledge on the x$, v$ and X$ (such
| as user$, fet$, obj$) tables/views.
|
| Are the following assumptions correct:
|
| x$
| if the sql parser sees an x$ table, it knows, it's not physically
| stored on harddisk (or tablespaces) but rather is referencing
| some bytes in memory. Therefor, it will return the values
| of the memory disguised as table data. They cannot be altered
| (using insert, updated and delete)
|
| v$
| the same goes for v$ views. The parser realizes these are not
| physically stored anywhere but are referencing data that the
| instance stores (or accumulates over time). They somethimes
| can be altered but this will not generate redo nor undo
| (as this is not data on the hd but in the memory)
|
| X$
| These tables are undistinguishable from ordinary (user created) tables.
| They reside on a tablespace (system); accordingly, these tables
| _could_ (but is not allowed to do by oracle inc.) be altered and would
| generate redo/undo if one did.
|
|
| I also understand, that if I issue a statement like
| create table XYZ (a number, b varchar2(34))
| this will somewhere translate into a
| insert into obj$ values (....,'XYZ',...)
| (though I am not 100% sure of this)
|
| But how can the table obj$ be created if this table must be
| around when (not if) the table is created.
|
| Anything?
|
| MK
Received on Tue May 28 2002 - 14:51:33 CDT
