You use the Storage tab to set data storage options for block storage databases.
If you want to change the I/O access mode (not use the mode specified in the “Current I/O access mode” box), in the “Pending I/O access mode” box, you select a mode:
Buffered I/O—Uses the file system buffer cache. If direct I/O was not specified for the DIRECTIO setting in the essbase.cfg file when the database was created, buffered I/O is the default. (See the Oracle Essbase Technical Reference.)
Direct I/O—Bypasses the file system buffer cache and performs asynchronous, overlapped I/Os, providing faster response time and greater potential to optimize cache sizes. If direct I/O is selected, Essbase attempts to use direct I/O each time that the database is started. If direct I/O is not available, Essbase uses buffered I/O. To enable use of the cache memory locking feature or the no-wait (asynchronous) I/O provided by the operating system, you must select direct I/O.
From the “Data compression” box, you select an option:
Bitmap encoding—A bitmap is used to represent data cells and only the bitmap, the block header, and other control information are stored on disk. This setting is the default and, usually, the most efficient method of compressing data.
Essbase stores only non-missing values and does not compress repetitive or zero values. When Essbase brings a data block into the data cache, it uses the bitmap to re-create missing values and, thus, fully expands the block.
RLE (Run-Length Encoding)—Consecutive, repetitive values, including zeros, are compressed, and a record is kept of each repeating value and the number of times that it is repeated consecutively.
RLE may be preferable if average block density is not greater than three percent or if the database includes many consecutive zero values or any consecutive, repeating value other than zero.
ZLIB—A data dictionary that is based on the data being compressed is created.
Usually, when data is extremely dense, ZLIB compression provides the best compression ratio. However, under some circumstances, other compression methods may yield better results. With ZLIB compression, the storage space that is saved has little or no relationship to the number of missing cells or the number of contiguous cells of equal value.
No compression
In the columns of the Disk Volumes table, you specify how storage is allocated on each disk volume:
Disk Volume—Select, in the order that you want volumes to be used, a series of volume names.
Partition Size—Specify the maximum amount of disk space to be allocated to each volume.
If you use the default (Unlimited), Essbase uses whatever it needs of the available space.
Unit—Select a unit (kilobytes, megabytes, or gigabytes) for each Partition Size value.
File Type—Specify, for each volume, whether to store index (essn.ind) files or data (essn.pag) files or both index and data files. The default is Index+Data.
File Size—For each volume, specify the maximum size that an index or data file can attain before Essbase creates a new file. The default is 2G; the minimum is 8192K (8M).
Unit—Select a unit (kilobytes, megabytes, or gigabytes) for each File Size value.
Delete button: Select the row containing the volume that you want to delete, and click Delete to stop Essbase from storing additional files on the volume. Essbase writes no new files to the volume but continues to access and use files previously created on the volume.
Note: | If you do not specify disk volumes for storage, Essbase stores all index and data files on the volume specified by the ARBORPATH environment variable and uses whatever space it needs. |
If you want no more files stored on a volume, in the Disk volumes table, select the row that contains the volume, and then click Delete. Although files can no longer be written to the volume, the files on the volume can be accessed and used.
The columns of the “Data/Index file” table provide information about each file stored on a disk volume:
Data/Index File Type—Either index (.ind) or data (.pag)
Size—In kilobytes
Status—Open, Closed, or Not Found
Name—Path and name
“Understanding Buffered I/O and Direct I/O” in the Oracle Essbase Database Administrator's Guide
“Allocating Storage and Compressing Data” in the Oracle Essbase Database Administrator's Guide
alter database (MaxL) in the Oracle Essbase Technical Reference
setdbstate (ESSCMD) in the Oracle Essbase Technical Reference
setdbstateitem (ESSCMD) in the Oracle Essbase Technical Reference
getperfstats (ESSCMD) in the Oracle Essbase Technical Reference