The Package Cache Hit Rate alarm becomes active when the package cache hit rate, expressed as a percentage, is low.
Package cache is memory that temporarily stores package and section information required for the execution of static and dynamic SQL statements. When applications obtain static SQL information from package cache, they eliminate I/O on system catalogs. When applications obtain dynamic SQL information from package cache, they avoid the cost of compiling the SQL statements.
Low package cache hit rate means that you are incurring more overhead to reload static SQL and recompile dynamic SQL.
The default thresholds are predefined as follows:
Threshold 1—The zero to 69 percent range. This raises High severity alarm stating, The package cache hit ratio is extremely low.
Threshold 2—The 70 to 79 percent range. This raises a Medium severity alarm stating, The package cache hit ratio is low.
Threshold 3—The 80 to 89 percent range. This raises a Low severity alarm stating, The package cache hit ratio is moderate.
Threshold 4—The 90 to 100 percent range. The package cache hit ratio is high. No alarms are raised.
The underlying metricsfor this alarm can be adjusted to suit your environment by using the Metric Editor.
You can consider increasing the size of package cache using the PCKCACHESZ database configuration parameter. If your database supports heavy transaction processing volumes, your current package cache size might not be able to accommodate these volumes.