Skip to Content
Former Member
Feb 07, 2011 at 11:58 AM

Index memory size vs disk size


Hi all,

I know the topic has already been discussed in the past, however, we still dont understand the memory size compared to the disk size of a BWA index.

Following information is output by TREXADMIN -> Index Maintenance:

Index-ID | Indextype | Mem Size [KB] | Disk size [KB] (Attributes)


bwp_bic:fzXYZ | logisch | 5587083 | 22477529

From our knowledge, the disk size of an index can be siginificantly higher than the "in-memory size" according to the following factors:

1. Deletions from the underlying InfoCube. Cause selective deletions are not performed in the BWA (instead rows are only marked as "deleted/dont use", the disk size can grow over time if lots of deletions occur and the index is never rebuild.

2. Index not loaded completely into main memory.



-> 1) The above information were about after a fresh rebuilt of the index! So no loads or deletions in between - the index was rebuit, and immediately had this "mismatch" between memory size and disk size.

-> 2) RSRV action "load all indexes into memory" was used prior to obtaining the above information!

So our question is:

WHY are the "mem size" vs. "disk size" figures so different by a magnitude???

and then:

WHICH figure is actually reliable to calculate how much memory the index is taking on a blade? SAP is internally using the "disk size" figure, however, this seems unreasonably high to us...

Thanks for clarifications!