Module ibm.jzos

Package com.ibm.jzos

Class ZFileRecordReader

java.lang.Object

com.ibm.jzos.RecordReader

com.ibm.jzos.ZFileRecordReader

All Implemented Interfaces:

ZFileConstants

public class ZFileRecordReader
extends RecordReader
implements ZFileConstants

This ZFile wrapper is no longer the most efficient way to read dataset records. Please see RecordReader.

In order to provide more efficient dataset record mode read performance, it is often beneficial to read a block, rather than a record, at a time from the underlying dataset. This class wraps an instance of ZFile, re-opens it with RECFM=U, and provides an interface for reading a record at a time. The underlying ZFile must have been opened with the following options:

• type=record
• read mode, either text or binary ("r", "rb" or "rt")

Reading the dataset a block at a time limits the number of calls to the C library fread() function and also reduces the number of JNI calls that need to be made. The z/OS XL C/C++ Programming Guide SC09-4765 (Chapter 34 - I/O Performance considerations) recommends taking this approach to increase performance when possible.

All record formats are supported, however performance gains will only be realized when the average record lengths are significantly less than the average block size.

Since:

2.3.0

See Also:

• RecordReader

Field Summary

Fields inherited from interface com.ibm.jzos.ZFileConstants

DEFAULT_EBCDIC_CODE_PAGE, DEVICE_DISK, DEVICE_DUMMY, DEVICE_HFS, DEVICE_HIPERSPACE, DEVICE_MEMORY, DEVICE_MSGFILE, DEVICE_OTHER, DEVICE_PRINTER, DEVICE_TAPE, DEVICE_TDQ, DEVICE_TERMINAL, DSORG_CONCAT, DSORG_HFS, DSORG_HIPER, DSORG_MEM, DSORG_PDS_DIR, DSORG_PDS_MEM, DSORG_PDSE, DSORG_PO, DSORG_PS, DSORG_TEMP, DSORG_VSAM, ERRNO_E_ABEND, ERRNO_E_DEFINEFILE, ERRNO_E_READERR, ERRNO_E_WRITEERR, ERRNO_EACCES, ERRNO_EILSEQ, ERRNO_EINVAL, ERRNO_EIO, ERRNO_EPERM, FLAG_DISP_MOD, FLAG_DISP_OLD, FLAG_DISP_SHR, FLAG_PDS_ENQ, LAST_OP_BSAM_BLDL, LAST_OP_BSAM_CLOSE, LAST_OP_BSAM_CLOSE_T, LAST_OP_BSAM_NOTE, LAST_OP_BSAM_OPEN, LAST_OP_BSAM_POINT, LAST_OP_BSAM_READ, LAST_OP_BSAM_STOW, LAST_OP_BSAM_WRITE, LAST_OP_C_CANNOT_EXTEND, LAST_OP_C_DBCS_SI_TRUNCATE, LAST_OP_C_DBCS_SO_TRUNCATE, LAST_OP_C_DBCS_TRUNCATE, LAST_OP_C_DBCS_UNEVEN, LAST_OP_C_FCBCHECK, LAST_OP_C_TRUNCATE, LAST_OP_HSP_CREATE, LAST_OP_HSP_DELETE, LAST_OP_HSP_EXTEND, LAST_OP_HSP_READ, LAST_OP_HSP_WRITE, LAST_OP_IO_CATALOG, LAST_OP_IO_DEVTYPE, LAST_OP_IO_LOCATE, LAST_OP_IO_OBTAIN, LAST_OP_IO_RDJFCB, LAST_OP_IO_RENAME, LAST_OP_IO_SCRATCH, LAST_OP_IO_SWAREQ, LAST_OP_IO_TRKCALC, LAST_OP_IO_UNCATALOG, LAST_OP_QSAM_FREEPOOL, LAST_OP_QSAM_GET, LAST_OP_QSAM_PUT, LAST_OP_QSAM_RELSE, LAST_OP_QSAM_TRUNC, LAST_OP_SVC99_ALLOC, LAST_OP_SVC99_ALLOC_NEW, LAST_OP_SVC99_UNALLOC, LAST_OP_TGET_READ, LAST_OP_TGET_WRITE, LAST_OP_VSAM_CLOSE, LAST_OP_VSAM_ENDREQ, LAST_OP_VSAM_ERASE, LAST_OP_VSAM_GENCB, LAST_OP_VSAM_GET, LAST_OP_VSAM_MODCB, LAST_OP_VSAM_OPEN_ESDS, LAST_OP_VSAM_OPEN_ESDS_PATH, LAST_OP_VSAM_OPEN_FAIL, LAST_OP_VSAM_OPEN_KSDS, LAST_OP_VSAM_OPEN_KSDS_PATH, LAST_OP_VSAM_OPEN_RRDS, LAST_OP_VSAM_POINT, LAST_OP_VSAM_PUT, LAST_OP_VSAM_SHOWCB, LAST_OP_VSAM_TESTCB, LOCATE_KEY_EQ, LOCATE_KEY_EQ_BWD, LOCATE_KEY_FIRST, LOCATE_KEY_GE, LOCATE_KEY_LAST, LOCATE_RBA_EQ, LOCATE_RBA_EQ_BWD, MODE_FLAG_APPEND, MODE_FLAG_READ, MODE_FLAG_UPDATE, MODE_FLAG_WRITE, OPEN_MODE_BINARY, OPEN_MODE_RECORD, OPEN_MODE_TEXT, RECFM_A, RECFM_B, RECFM_F, RECFM_M, RECFM_S, RECFM_U, RECFM_V, S_IRGRP, S_IROTH, S_IRUSR, S_IRWXG, S_IRWXO, S_IRWXU, S_ISGID, S_ISUID, S_ISVTX, S_IWGRP, S_IWOTH, S_IWUSR, S_IXGRP, S_IXOTH, S_IXUSR, SEEK_CUR, SEEK_END, SEEK_SET, VSAM_TYPE_ESDS, VSAM_TYPE_ESDS_PATH, VSAM_TYPE_KSDS, VSAM_TYPE_KSDS_PATH, VSAM_TYPE_NOTVSAM, VSAM_TYPE_RRDS

Method Summary

Modifier and Type	Method	Description
void	close()	Close the reader and underlying ZFile.
int	getBlksize()	Answer the BLKSIZE, which is the maximum block length supported by the dataset.
String	getDDName()	Answers the DD name used to open the underlying dataset.
String	getDsn()	Answers the native dataset's absolute name, or name(member) if the native dataset is a member of a PDS.
int	getLrecl()	Answer the LRECL, which is the maximum record length for variable length files.
String	getRecfm()	Get the native file's record format.
int	getRecfmBits()	Answer the RECFM bits
static ZFileRecordReader	newReader(ZFile zFile)	Deprecated. This method no longer provides the most efficient way to perform dataset I/O.
int	read(byte[] buf)	Read a record from the native file into a buffer.
int	read(byte[] buf, int offset, int len)	Read a record from the native file into a buffer.

Methods inherited from class com.ibm.jzos.RecordReader

getAutoFree, newReader, newReaderForDD, setAutoFree

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

newReader

@Deprecated
public static ZFileRecordReader newReader(ZFile zFile)
                                   throws ZFileException

Deprecated.

This method no longer provides the most efficient way to perform dataset I/O.

Construct a new ZFileRecordReader on the given ZFile, which must have been opened in read, record mode.

Throws:

ZFileException

See Also:

• RecordReader.newReader(String, int)
• RecordReader.newReaderForDD(String)

read

public int read(byte[] buf)
         throws ZFileException

Read a record from the native file into a buffer.

Specified by:

read in class RecordReader

Parameters:

buf - the byte array into which the bytes will be read

Returns:

the number of bytes read, -1 if EOF encountered.

Throws:

ZFileException - if the native call fails

read

public int read(byte[] buf,
 int offset,
 int len)
         throws ZFileException

Read a record from the native file into a buffer.

Specified by:

read in class RecordReader

Parameters:

buf - the byte array into which the bytes will be read

offset - the offset, inclusive in buf to start reading bytes

len - the number of bytes to read

Returns:

the number of bytes read, -1 if EOF encountered.

Throws:

ZFileException - if the native call fails

close

public void close()
           throws ZFileException

Close the reader and underlying ZFile.

Specified by:

close in class RecordReader

Throws:

ZFileException - if the native call fails

getBlksize

public int getBlksize()

Description copied from class: RecordReader

Answer the BLKSIZE, which is the maximum block length supported by the dataset.

Specified by:

getBlksize in class RecordReader

getDDName

public String getDDName()

Answers the DD name used to open the underlying dataset. Returns null unless this instance was created by RecordReader.newReaderForDD(String)

Specified by:

getDDName in class RecordReader

Returns:

String ddname

getDsn

public String getDsn()

Description copied from class: RecordReader

Answers the native dataset's absolute name, or name(member) if the native dataset is a member of a PDS.

Specified by:

getDsn in class RecordReader

Returns:

String dataset name

getLrecl

public int getLrecl()

Description copied from class: RecordReader

Answer the LRECL, which is the maximum record length for variable length files.

Specified by:

getLrecl in class RecordReader

getRecfm

public String getRecfm()

Description copied from class: RecordReader

Get the native file's record format.

Specified by:

getRecfm in class RecordReader

See Also:

• ZFile.getRecfm()

getRecfmBits

public int getRecfmBits()

Description copied from class: RecordReader

Answer the RECFM bits

Specified by:

getRecfmBits in class RecordReader

See Also:

• ZFile.getRecfmBits()