ora-00604 and ora-01653

Hi:

I was getting folloing error. I was able to resolve with increaing the size of SYSTEM tablespace.

Error in execution of OCI function OEXEC, OEXN:
ORA-00604: error occurred at recursive SQL level 1
ORA-01653: unable to extend table SYS.IDL_SB4$ by 13 in tablespace SYSTEM

I have few questions,
1)why am I getting error ora-00604?
2)what should be ideal size for a SYSTEM tablespace for oracle 8.1.6?
3)When IDL_SB4$ table is used?

Thanks.

ORA-00604 error occurred at recursive SQL level string
Cause: An error occurred while processing a recursive SQL statement (a statement applying to internal dictionary tables).
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1. As you can see this is an error that relates to internal dic. tables, ie system ts.
2. There is nothing like an ideal size. If you have a large db, like DW or DSS, you would have a large data dic. tables, thus requiring a large SYSTEM ts. I suggest you turn on Autoextend for the System ts. The System ts is a slow growing ts and should be allowed to grow by itself w/o DBA interference.
3. no clue, check on Metalink.