ASE 12.5 uses more memory than previous releases. ASE now allocates more memory for the dataserver, procedure cache, and named caches. If you do not increase physical and/or shared memory, the additional needed memory will be taken from the default data cache, possibly affecting performance. Check the installation guide for minimum memory requirements. Use sp_helpcache to check cache sizes before and after upgrade. Adjust memory if necessary to restore the original value of the default data cache after upgrade.
See the System Administration Guide for information on configuring memory and data caches; see the Performance and Tuning Guide for more information on memory issues.