Storage
Stream Storage
StreamA Storage Stream is a column in a PegaRULES database table that contains property data in a compressed format. Most tables in the database contain a Storage Stream column, identified as the pzPVStream column.
Don't confuse the Storage Stream with stream
processing, an unrelated feature than involves generating HTML (or XML)
text from HTML rules, XML Stream rules, and other rule types.
In Oracle, Microsoft SQL Server and most other database vendor software, the Storage Stream is stored as a binary large object or BLOB data type.
For example, an aggregate such as a Value List property
can have multiple values. When the system saves an object that includes
an aggregate property, its values are compressed together (or
"deflated") into a single column. When the instance is later
opened and placed on a clipboard, the column is decompressed (or
"inflated").
When deflated, the property names and values are present in a single text value. This text value has a proprietary format; the values are obfuscated. CLINB 4/21/06
For guidance on understanding the space requirements of the storage
stream articles, see the Pega Developer Network article 
PRKB-12464 How to estimate disk space requirements for a
PegaRULES database (Oracle).
Values of the Storage Stream column (pzPVStream) may
require a large number of bytes of storage, and extracting or updating a
property value from this column requires that the entire value be
transmitted from the PegaRULES database to the server. Accordingly,
careful design to minimize the number of Storage Stream operations can
improve performance significantly.
The PEGA0004, PEGA025, PEGA0039 and PEGA0040 alerts call attention to BLOB issues that can affect overall system performance.
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