Storage Stream
A 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 PDN article 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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