Integrated Storage Manager
The Integrated Storage Manager detects problems before they became serious errors such as loops or out-of-storage conditions. The Integrated Storage Manager enforces storage management rules to avoid the loops and 878/40d abends. A storage constraint is signaled when a storage constraint rule is violated.
When Db2 Query Monitor defines its virtual spaces, it defines storage constraint rules. Some examples of these rules include:
- No more than 4096 nesting levels per Db2
- A maximum SQL text allocation per Db2
- A maximum SQL text allocation per Query Monitor Subsystem
- No more than 1024 open sections per open thread
- No more than 1024 host variables per section
- No more than 2G total in storage (by default)
When a storage constraint rule is violated, the Integrated Storage Manager does not allow any additional storage to be obtained for that type of constrained storage. For example, if thread 1000 attempted to acquire its 1025th section, a storage constraint would be signaled. However, if thread 2000, attempted to acquire its 50th section, it would be allowed.
Storage constraints only impact the violator. When a storage constraint is signaled, a diagnostic entry is created. This constraint is defined by Db2 Query Monitor to avoid a runaway condition that leads to an auxiliary storage shortage.
The Integrated Storage Manager is part of the base Db2 Query Monitor product and does not require activation.