Example of setting buffer cache sizes

The following table lists factors that may consume memory for your system and shows an example of how much remains for your main and temp buffer caches. This example assumes that the system has 1GB of physical memory, no other significant applications on the hardware other than running Sybase IQ, and only one active database at a time. The table gives separate figures for the primary type of database access: queries or inserts.

**Table 4-1: Example of memory (in MB) available for buffer caches**
Memory use	Amount used	Memory available: Queries	Memory available:Inserts
Total amount of physical memory available (approximate in MB)		1000	1000
Operating system use assuming a minimum amount for a UNIX system	100^a	900	900
Overhead for number of active users: approximately 30 connected users but only about 10 active at 10MB each	100	825
Overhead for inserts from flat files assuming a 200-byte record size and default settings	97		828
Memory remaining for the main and temp buffer caches		675	828
iqmc (Main_Cache_Memory_MB) setting: 60% of memory remaining for buffer caches		405	497
iqtc (Temp_Cache_Memory_MB) setting: 40% of memory remaining for buffer caches		270	331

^aMinimum operating system use for Windows is 30MB

As shown in the table, you should have one set of values for your buffer caches when primarily inserting into the database, another set when primarily querying the database, each differing from a typical mixed load of inserting and querying. To change the cache sizes, see “Setting buffer cache sizes.” Remember that the cache size options do not take effect until you stop and restart the database.