INITRANS is a block level storage parameter which can be specified while creating a object (table). INITRANS and MAXTRANS parameters are used to control the concurrent access to the same block. There can be a maximum of 255 concurrent sessions that can access a block at any given time. So the maximum value for MAXTRANS parameter is 255. The value specified through INITRANS are taken into consideration for creating the initial number of ITLs (Intersted Transaction Entries) in the block.
While creating the table if INITRANS 20 is specified, then 20 different ITL slots will be created in the block transaction variable header.
BLOCK SIZE and INITRANS :
Each and every ITL entry in the block transaction variable header takes 24 bytes. Though a block can have a maximum of 255 different ITLs , the block is quite limited to allocate only some defined ITLs in the header. The database block size plays a important role in allocating the number of inital ITLs for the blocks.
The rule is “the total size allocated for initial ITLs SHOULD be LESS THAN 50% of the database block size”
ie : sizeof(INITIAL ITLs) < ( 50 % of the DATABASE BLOCK SIZE )
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