PC_POOLSIZE default 127
PC_HASHSIZE default 31

onstat -g prc позволяет посмотреть текущие значения.

Для 7.3 admin guide пишет
Administrator’s Guide for Informix Dynamic Server 7.3

Stored Procedures Cache
When a session needs to access a stored procedure for the first time, the
database server reads the stored procedure from the system catalog tables.
The database server converts the stored procedure into executable format
and stores the procedure in a cache, where it can be accessed by any session.
The size of the stored procedure cache is not configurable.

Для 9.x
Administrator’s Guide for Informix Dynamic Server.2000

SPL Routine and the UDR Cache
The database server converts an SPL routine to executable format and stores
the routine in the UDR cache, where it can be accessed by any session.
When a session needs to access an SPL routine or other user-defined routine
for the first time, the database server reads the definition from the system
catalog tables and stores the definition in the UDR cache.
You can configure the size of the UDR cache with the PC_HASHSIZE and
PC_POOLSIZE configuration parameters. For information about changing the
default size of the UDR cache, refer to the chapter on queries and the query
optimizer in your Performance Guide.

В таком вот аксепте