The converter is where the database system keeps information about which logical page number is saved at what physical position (MaxDB block address).
Converter entry
271397 P 1/0000271404
The logical page number 271397 is a permanent (P) data page. It is stored in the first volume at block address 271404.
Types of Data Pages
Type |
Description |
P |
Permanent data page |
S |
Data page in a SAP liveCache database instance |
T |
Temporary data page |
When the database system fails to find a page number in the data cache, it searches for the page number in the converter and uses this to calculate the physical position of the data page in the data volumes.
The converter uses the shadow storage concept. This means that the database system stores the database state from the last savepoint on shadow pages. When pages are changed, the database system first creates copies of the changes pages. Once the database system has written the changed pages to the data area at a savepoint and the savepoint is complete, the shadow pages are released to be overwritten.
Pages are never displaced from the converter. If necessary, the database system allocates additional pages from the I/O buffer cache to the converter. You are, therefore, unable to configure the size of the converter explicitly.
When the database system writes the converter to the data area at a savepoint, it gives the converter a version number. The converter saved at the next savepoint is then given the next higher version number.
All concurrently-active users use the converter jointly.
See also: