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S Glossary
296 U929-J-Z125-9-76
snap pair, snap pubset, snap session, snap unit
A snap unit is the copy of an (original) unit (logical disk in BS2000/OSD) at a
particular time (“Point-in-Time copy”). The TimeFinder/Snap component
creates this copy as a “snapshot” in accordance with the “Copy-On-First-Write
strategy“: Only if data is modified is the original data concerned written
beforehand into a central save pool of the Symmetrix system. The snap unit
contains the references (track pointers) to the original data. In the case of
unmodified data the references point to the unit, in the case of modified data to
the save pool.
After they have been activated, the unit and snap unit are split; applications can
access both.
The unit and snap unit together form a snap pair. TimeFinder/Snap manages
this pair in what is known as a snap session.
If snap units exist for all units of a pubset, these snap units together form the
snap pubset.
Details of this are provided in the manual "Introductory Guide to Systems
Support".
sort key table
Table pointing to the member records of a set occurrence.
source program
Program written in a programming language and not yet translated into machine
language.
spanned record
Record exceeding the length of a page. Only UDS/SQL-internal records can
be spanned records;
User record types must not exceed
– 2020 bytes for a page length of 2048 bytes
– 3968 bytes for a page length of 4000 bytes
– 8064 bytes for a page length of 8096 bytes.
SQL
SQL is a relational database language which has been standardized by ISO
(International Organization for Standardization).
SQL conversation
See conversation.
SQL DML
SQL Data Manipulation Language for querying and updating data.