17.10 - Usage Notes - Advanced SQL Engine - Teradata Database

Teradata Vantageā„¢ - SQL External Routine Programming

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1147-171K
Language
English (United States)

Read-only GLOP data can be split into a number of pages, each of which can be overlaid with the current GLOP data in memory. The page to initially map for read-only GLOP data can be specified when the GLOP is added or changed. Read/write or globally modifiable GLOP data can only consist of one page. Remapping page one of such a GLOP will remap the original data contents of the GLOP. Any changed data in the read/write page is thrown away.

All read-only pages are the same size and depend on the GLOP_Length field of the GLOP set row.

The GLOP read/write data must not be locked when this call is made. It places an internal exclusive lock that blocks all read and write locks while a page is being replaced.

Rules to be aware of:

  • You can map the same type of GLOP data in multiple map indexes for read-only GLOP data. That way you can map different pages of the same GLOP data at the same time. This has to be set up that way in the GLOP_Map table. This cannot be done for 'RO', 'US' or 'XR' GLOPs.
  • When reloading page one map for a read write GLOP, an automatic write lock is placed to prevent any external routine from reading or writing the GLOP while the data is being reinitialized with the original contents. If you use this as part of the design, make sure that all external routines are aware that this could happen.
  • Different pages for read-only GLOP data can be mapped by different external routines at the same time.