If you have reason to think that Search is underestimating the size of your index, you can manually adjust the size of physical partitions.
For example, estimation says that your content requires three physical partitions, but you know that you are very close to needing four. To rule out any potential performance problems, you overrule the estimation and create four partitions instead. If this happens often, you may want to adjust the fullnessOfRecommendedPartitions setting in the /atg/search/routing/RoutingIndexService.properties file to some number less than one, as shown:
fullnessOfRecommendedPartitions=0.7
Going forward, Search will estimate your content based on 70% of the maximum physical partition size, making it less likely that your partition will fill up.
Instead of using multiple partitions for large content, you may want to increase the partition size. Increasing partition size reduces the number of partitions and engines required, which can improve query time; however, it can also increase indexing time when using parallel engines. To increase the partition size, change the MemoryReserveSize property in the AEConfig.xml file. This setting controls how large a partition can be. The default setting is 0x54000000 (1.4 GB), which is the maximum for Windows 32-bit systems. This can be increased on 64-bit platforms to as much RAM is available, divided by the number of engines on the host (the maximum number of engines can be configured in the environment; see Managing Search Environments). Some suggested sizes include:
2 GB (maximum for Linux 32-bit)
<MemoryReserveSize>0x80000000</MemoryReserveSize>4 GB
<MemoryReserveSize>0x100000000</MemoryReserveSize>8 GB
<MemoryReserveSize>0x200000000</MemoryReserveSize>
