The Statistics tab displays information about data blocks, hit ratios, and read/write operations.
Several nodes display basic information about the current run of the database:
Database start time—According to the time zone of Essbase Server
Database elapsed time—In hours:minutes:seconds
Number of connections—Number of connected users
Statistics—Date and time that Essbase last collected information for the Statistics tab, according to the time zone of Essbase Server
The Blocks node displays statistics about the data blocks of a block storage database:
Number of existing blocks—Total number of blocks that exist (contain data)
Block size—Size, in bytes, of each expanded (decompressed) data block (number of cells * 8; ideally, between 8 and 100 kilobytes). To alter block size, you must change the dense-sparse configuration of the database.
Potential number of blocks—Maximum number of blocks (derived by multiplying the number of members of one sparse dimension by the number of members of another sparse dimension and so on). For example, the Sample Basic database contains 19 Product members and 25 Market members (not counting shared or label-only members). Because Product and Market are sparse dimensions that store data, there are 19 x 25 = 475 potential data blocks.
Existing level 0 blocks—Total number of level 0 blocks (blocks whose sparse dimension members have no children) that exist (contain data). Because data can be loaded at upper levels, level 0 blocks and blocks that are created by data input are not necessarily the same.
Existing upper-level blocks—Total number of non-level 0 blocks that exist (contain data). Upper-level blocks include all combinations of upper-level sparse members plus upper-level combinations that include level 0 sparse members.
Block density (%)—Average percentage fill of data points within each data block, based on a sample of existing data blocks. Dense-sparse configuration should maximize block density. Maximizing block density, however, may result in proliferation of data blocks. Block size and block proliferation considerations may overshadow the attempt to maximize block density.
Percentage of maximum blocks existing—Percentage that compares the number of blocks that exist and the number of potential blocks. The percentage is a measure of the sparsity of the database. It is not uncommon for the percentage to be very small; for example, less than 1 percent.
Compression ratio—Measure of the compression efficiency of blocks stored on disk. The compression ratio usually indicates block density.
Average clustering ratio—Fragmentation level of data (.pag) files. The maximum value, 1, indicates no fragmentation. If you are experiencing degraded retrieval, calculation, or data load performance and the clustering ratio value is significantly less than 1, consider forcing a rewrite of data files by exporting and reloading data. Rewriting files defragments the files, resulting in a clustering ratio closer to 1.
The “Aggregate storage statistics” node displays statistics about each dimension of an aggregate storage database:
Name
Number of stored levels (dimension level factor)—In aggregate storage databases, not all levels are stored.
Number of bits used in the dimension key—Key length is a multiple of 8 bytes (for example, 8, 16, or 24). Therefore, for example, a key that uses 65 bits has a key length of 9 bytes, and a key that uses 64 bits has a key length of 8 bytes. Therefore, if you reduce the number of bits used to 64, you reduce the size of the database.
The “Aggregate storage statistics” node displays statistics about an aggregate storage database:
Max. key length (bits)—Sum of all bits used by all dimensions (For example, the key used for all dimensions contains 20 bits, and the first 4 are used by Year.)
Max. key length (bytes)—Number of bytes that the key uses per cell
Number of input-level cells—Assuming that all input-level cells are level 0 cells
Number of aggregate views
Number of aggregate cells
Input-level data size (kilobytes)—Total disk space used by input-level data
Aggregate data size (kilobytes)—Total disk space occupied by aggregate cells
When reviewing the runtime statistics that are displayed in the Run-time node, consider the following information about hit ratios:
A hit ratio is a percentage that identifies how often information is retrieved from a cache, rather than from disk.
As the hit ratio increases, performance improves, because less information is retrieved from disk.
A hit ratio of 1.0 identifies maximum performance, because data is never retrieved from disk.
It is recommended that you allocate memory to caches in small increments. Small and large allocations may produce the same benefit, and large allocations usually have limited effect on the hit ratio.
For block storage databases, the Run-time node displays various hit ratio statistics:
Hit ratio on index cache
Hit ratio on data file cache
Hit ratio on data cache
For aggregate storage databases, the Run-time node displays statistics about the aggregate storage cache:
Cache hit ratio
Current cache size (KB)—The cache grows dynamically up to the specified limit.
Current cache size limit (KB)—To change the limit, see Sizing the Aggregate Storage Cache.
For block storage databases, the Run-time node identifies the number of times each of the following events occurred and provides path information about the affected data files.
Index page reads
Index page writes
Data block reads
Data block writes
For aggregate storage databases, the Run-time node displays statistics about pages:
Page reads since last startup
Page writes since last startup
Page size (KB)
For aggregate storage databases, the Run-time node displays statistics about disk space (“Disk space” refers to the space used in the Default tablespace, and “Temporary disk space” refers to the space used in the Temp tablespace. In both cases, some space within some files may not be used.):
Disk space allocated for data (KB)
Disk space used by data (KB)
Temporary disk space allocated (KB)
Temporary disk space used (KB)
“Optimizing Essbase Caches” in the Oracle Essbase Database Administrator's Guide
display database (MaxL) in the Oracle Essbase Technical Reference
query database (MaxL) in the Oracle Essbase Technical Reference
getdbstats (ESSCMD) in the Oracle Essbase Technical Reference
getperfstats (ESSCMD) in the Oracle Essbase Technical Reference