What are INITRANS and MAXTRANS transaction entry parameters?
What are INITRANS and MAXTRANS transaction entry parameters?
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The INITRANS transaction entry parameter specifies the number of DML transaction entries (default value is one for table data blocks and two for index and cluster data blocks) for which space is initially reserved in the header of each data block allocated to a database object. When multiple transactions access a data block, each transaction is allocated space in the header of the data block. Once the space reserved by INITRANS is depleted, the space for additional transaction entries is allocated out of the free space in the data block. Once allocated, this space becomes a part of the data block's header, and it is never freed. To avoid this, the MAXTRANS transaction entry parameter is used.
The MAXTRANS parameter specifies the maximum number of concurrent DML transactions (default is operating system dependent) that can ever access a data block. Therefore, by using the MAXTRANS parameter, the amount of free space that can ever be allocated for transaction entries in a data block can be limited.
The maximum number of concurrent transactions that can access a data block is 255.
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