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onstat -g rbm Block Map for Resident Segment

The onstat -g rbm command displays a block map for the resident segment of shared memory.

Block bitmap for resident segment address 0x44000000:
 address = 0x44000730, size(bits) = 3733836
 used = 3733833, largest_free = 3

      0:ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
    256:ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
    512:ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
    768:ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff

Output Description

Heading Description Format
bitmap In-memory starting address of the used/free blocks in the segment Hex
bitmap size The number of bytes in the block bitmap Dec
address/data Starting address followed by 32 bytes of data Hex/Hex
used The total number of bits in the bitmap that are set to 1 Dec
largest_free If this is a value other than -1 it is the largest number of consecutive bits that are free Dec

Notes

    Each bit (1:Used 0:free) of the bitmap represents a 4K block.

    Multiply used/largest_free by 4K to get total memory used

    If the largest_free has not been calcaluted then largest_free space will be -1. The largest_free space is maintained on a per memory request basis, it is only calculated when the instance tries to allocate a set of blocks starting at the lastalloc block but there is not enough free space. It is reset to -1 as soon as another block is allocated in the segment.

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