SQL/MX 2.x Reference Manual (G06.24+, H06.03+)

SQL/MX Utilities
HP NonStop SQL/MX Reference Manual—523725-004
5-24
Considerations for import
DDL Locks
When import uses the fast insert technique, a DDL lock is held on the object for the
entire duration of the operation. This strategy prevents any concurrent import
operation or any DDL or utility operation on this table until the first import using the
fast insert technique is complete. If you use multiple import processes to load different
partitions of an empty table that meets the described criteria, only the first import
operation would be able to use the more efficient fast insert technique. You should start
the remaining import operations after the first one completes and VSBB inserts will
be used with TMF transactions
If the import operation fails unexpectedly, you must run the RECOVER utility to remove
the DDL lock and perform cleanup. For expected errors, error handling will ensure that
the data in the table is purged.
Recovery
If import fails, you must run the RECOVER utility command to clean up the failed
operation.
If the import fails to reset the audit attribute of the table that was altered during the
operation, specify RECOVER with the CANCEL or RESUME option to reset the audit
attribute. If import fails after successful data insertion and fails to reset the audit
attribute, specify RECOVER with the RESUME option. If import fails before the data is
successfully inserted, specify the RECOVER with the CANCEL option to remove the
DDL lock and remove partial data if inserts were not done. You can find this information
by reading the DDL_LOCK table. If you run the RECOVER operation with the incorrect
option, RECOVER displays an error message so you can rerun it with the correct
option. For information, see Checking File Locks on page 5-3.
If the import operation fails unexpectedly, triggers that were disabled prior to running
import are not reenabled by the RECOVER utility. You must reenable them. For
expected errors, error handling ensures that triggers are reenabled.
No restart facility is available to handle partially copied data.
Concurrency
If you are importing into an empty table or if the target table does not have index or
referential integrity constraints, import uses fast loading techniques. Concurrent
import operations are not allowed. Concurrent DML, DDL, and utility operations are
also not allowed.
If import is not using fast loading techniques, all DML operations (SELECT, UPDATE,
DELETE, INSERT) can be performed concurrently. If too many locks are on the
partition, DP2 escalates to a table lock, which prevents concurrent DML operations.
Utilities that read only metadata (EXPORTDDL, INFO, MXGNAMES, SHOWDDL,
SHOWLABEL, VERIFY) can be performed concurrently.
Parallel imports on the same table are allowed. DDL operations are not recommended.