undo

Resource allocation when importing a yago2 ontology into an oracle semantic database


This is a short review of the resources nessecary when importing a full yago2 ontology, which is about 200 mio triples, into an oracle semantic database. Some information and snippets about the way to execute the import is given but this is not the main focus of the article. I’m still on a fresh, not otherwise loaded 11gR2.0.1 database.

The way to execute the import mainly followed the instructions given with the rdf demos, that is using sqlldr and bulkload.ctl to populate a staging table as proposed in ORACLE_HOME\md\demo\network\rdf_demos and afterwards employ sem_apis.bulk_load_from_staging_table() to actually load the data into the sematic net. bulkload.ctl has in fact not being changed anyway, the yago2 data being supplied in nt triples formatting like this:

<Embeth_Davidtz> <http://yago-knowledge.org/resource/actedIn> <Army_of_Darkness> .

and the staging table:

create table yago2_stage (
  RDF$STC_sub varchar2(4000) not null,
  RDF$STC_pred varchar2(4000) not null,
  RDF$STC_obj varchar2(4000) not null,
  RDF$STC_sub_ext varchar2(64),
  RDF$STC_pred_ext varchar2(64),
  RDF$STC_obj_ext varchar2(64),
  RDF$STC_canon_ext varchar2(64)
) compress;

and the sql loader call:

sqlldr userid=lucene/*** control=yago2.ctl data=yago2_1.nt direct=true skip=0 load=95000000 discardmax=10000 bad=yago2.bad discard=yago2.dis log=yago2.log errors=0

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Recovering disk failures that comprise undo segements


This is just a snapshot of some sitation that happened quite a while ago on a 10g oracle database. I’m not going to dive into the details that much, just providing some selects to decipher the scenario and show up one of the probable ways of resolving the problem.

Jep, due to a disk failure, as i noticed during the analysis, some statements and things complained about datafiles being offline. An attempt to re-online some datafile resulted in an ORA-00376 error as follows:

SQL> ALTER DATABASE DATAFILE 'H:\app_ORACLE\SAN_4\ORADATA\appxyz\stuff\app_UTL_06.DBF' ONLINE;
ALTER DATABASE DATAFILE 'H:\app_ORACLE\SAN_4\ORADATA\appxyz\stuff\app_UTL_06.DBF' ONLINE
*
FEHLER in Zeile 1:
ORA-00376: Datei 6 kann zur Zeit nicht gelesen werden
ORA-01110: Datendatei 6: 'H:\app_ORACLE\SAN_3\ORADATA\appxyz\UNDOTBS03.DBF'

Looking up dba_data_files produced this output:

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